MAGS WEBS WORKSHOP SUMMARY
Henry Leighton, Geoff Strong, Peter di Cenzo
1. Introduction
One of the stated aims of the Canadian contribution to GEWEX is to "Understand and model the
high latitude water and energy cycles that play roles in the climate system". MAGS, through its
observational and modelling studies, should be making a major contribution to achieving this
goal. We are now well into MAGS-2 and so this is an appropriate time to assess where we stand
towards achieving this objective with respect to the Mackenzie basin. Are we on track? Are
there studies that we should be undertaking over the next three years in order to make sure that
we do as well as we can to achieve this goal? The purpose of the WEBS (Water and Energy
Balance Study) Workshop, which was held at the MSC Headquarters in Toronto, was to try to
answer these questions. The first day of the workshop was devoted to individual presentations
which were led-off with overviews of the water and energy budgets by Geoff Strong and Kit
Szeto, respectively. The second day started with two parallel breakout sessions, one devoted to
water and the other to energy, followed by a general discussion of the current state of knowledge
and future plans. The workshop program is attached as Appendix I, and the list of participants is
in Appendix V.
2. Overview Presentations
2.1 Water Budget (Geoff Strong)
Results demonstrate near-closure of the MAGS water budget at the monthly and annual
timescales, with about a 10% difference between the annual basin atmospheric and hydrologic
water budgets. There are still some tasks that may improve the results – for example, including
river channel features from Hick’s work improves the agreement between modelled and
observed river flow. Strong emphasized the importance of estimating the uncertainties in the
various components of the moisture budget and presented an analysis of the sources of
uncertainty.
2.2 Energy Budget (Kit Szeto)
MAGS water balance studies are ahead of energy balance studies, and small-scale energy budget
studies are ahead of large-scale studies. Information on long-term variability is lacking. There
are more modelling/analysis studies than observational studies.
Szeto identified several areas where there are important gaps. On the observations side, other
than observations of incoming longwave radiation at specific local sites (for example, Great
Slave Lake), there are essentially no systematic direct measurements nor satellite retrievals of the
longwave radiation fields over the Mackenzie Basin. We know little about the vertical cloud
structure. We have few measurements of surface energetics for different surface types. And
finally, as with the moisture budget work, there has been insufficient emphasis on error analysis.
On the modelling and analysis side, model resolution is not as high as one would like, model
physics has to be improved and tested, and data assimilation techniques have to be advanced.
Szeto also emphasized that it is important to remember that the water and energy cycles are
coupled and feedback on each other and that it is a mistake to think in terms of two separate
cycles.
3. Research Presentations
There were 13 research presentations covering many aspects of WEBS, some from a modelling
perspective and others which were based on observations, most of which were followed by lively
discussion. Presentation titles and authors are indicated in the workshop program (Appendix I).
4. Breakout Sessions
4.1 Water Budget Sub-Group (Chair: Geoff Strong)
Participants in the Water Budget Sub-Group were asked to consider to what degree can we close
the water budget for MAGS. The approach taken for GCIP (GEWEX Continental-scale
International Project) has been to compute the water budget using half a dozen models, and then
use the ensemble average. Can we measure all the necessary variables? On the ‘basin scale’,
what are the numbers? How well can we model these at annual and monthly timescales? For the
limited time available in the breakout session, the group consensus was to work through the
WEBS Progress Chart (Appendix II) for all water-related variables. A tactical issue was raised
regarding how can we represent these numbers in useable form? A summary of approximate
lower limits for water-related variables, including additional variables not identified in the
original chart is presented in Appendix III.
4.2 Energy Sub-Group (Chair: Henry Leighton)
The discussion in the atmosphere group focussed on the WEBS Progress Chart as a way of
summarizing our current level of understanding of the energy budget. It quickly became apparent
that it was not possible to make meaningful statements about the various budget terms within the
time constraints of the breakout session. Instead, those present agreed to divide the table up and
assume responsibility for submitting a few sentences about our understanding of one or more of
the table fields shortly after the workshop. The edited responses are attached as Appendices IV
and V.
5. Wrap Up Session
The workshop ended with a general discussion about problems and progress. Subsequent to the
workshop it was decided to set up a team of MAGS scientists who would take on the
responsibility of advancing MAGS-WEBS.
2
The following are some of the comments from the general discussion:
Ron Stewart:
• MAGS needs someone to lead WEBS effort or it won’t be done. SC should think about
designating someone as “Mr/Mrs WEBS” to lead the effort.
Hok Woo:
• We need a more aggressive effort to attack problems.
Ric Soulis:
• Significant milestone – RCM is almost ready to be fully coupled with WATCLASS. We can
circulate results from model runs for comments/discussion. This would be a good starting
point and it reflects all of our work.
Yves Delage:
• We should look at constructing what we think has been observed to test its goodness in the
observation validation process – look at current climate, not just future.
Wayne Rouse:
• A lot has been done since MAGS-1 – ideas have matured, CAGES has matured.
• Having everyone prepare 1-2 paragraphs on their WEBS contribution is a great idea and
would not be a major effort to do so.
Geoff Strong:
• One big problem is that we work at vastly different temporal and spatial scales.
• We all need to do error analysis for our results.
John Gyakum:
• We need to consider spatial errors – moisture paths can be missed, not just vertically but also
horizontal transport.
• Trying to close our budgets lead us to identification of greater problems.
• Focus during breakout session was useful.
Kit Szeto:
• We need to decide upon a preferred format – common units and formats very important.
Paul Louie:
• Can we close budget better than the worst parameter? We need to decide on level to work at.
Normand Bussieres:
• A tool to get a handle on uncertainties is to make use of higher spatial resolution instruments
on new satellites – will allow remote sensing to get a handle on variables in the basin.
Bill Schertzer:
• We need to determine averaging scales.
3
Alexander Trischenko:
• Satellites measure at TOA. It is difficult to determine profiles, albedo, atmospheric moisture,
etc. – need to develop algorithms.
• EOS, TERRA, AQUA will provide useful data for MAGS.
ShuSen Wang:
• Current CCRS products not fully used, or sometimes not used at all – need closer
collaborations to get products fully utilized.
Hok Woo:
• Will be visiting CCRS and Josef Chilar in June – will ask Josef for a list of products.
Anne Walker:
• We have not looked fully at what remote sensing can do for MAGS. We need to see what
new satellites have that are useful for MAGS.
• We need error analysis for remote sensing products.
Bruce Davison:
• For someone new to MAGS, like myself, the breakout process was very useful.
Brenda Toth:
• It sometimes seems somewhat overwhelming working at the point scale and then trying to
represent it at a grid scale.
Acknowledgements
This meeting was supported by Environment Canada, and the Natural Sciences and Engineering
Research Council of Canada. The workshop organizing committee comprised Henry Leighton
and Geoff Strong. Kit Szeto and Bob Crawford are thanked for their excellent efforts in handling
the logistics of the workshop, and MSC-Downsview for hosting the meeting.
4
APPENDICES
A1. Program for the MAGS-WEBS Workshop.
A2. MAGS WEBS Progress Chart.
A3. WEBS Progress Chart – Water Budget Sub-Group.
A4. Inputs to MAGS WEBS Progress Chart – Energy Budget Sub-Group.
A5. The Water and Energy Budgets of Lakes – Components Overview:
Measurements, Modelling and Research Gaps.
A6. List of Workshop Participants.
5
APPENDIX I
Program for the MAGS-WEBS Workshop
AMSWD Boardroom, MSC-Downsview, May 27-28, 2002
MONDAY, MAY 27
8:45 - 9:25
Coffee, tea or juice
9:25 - 9:30
Welcome and Introductory Remarks (Henry Leighton)
SESSION 1
OVERVIEW PRESENTATIONS (9:30 - 10:20)
(Chair: John Gyakum)
9:30 - 9:55
Overview of Water Budget Studies - Current status: modelling and
observations. (Geoff Strong)
9:55 - 10:20
Overview of Energy Budget Studies - Current status: modelling and
observations. (Kit Szeto)
SESSION 2a
INDIVIDUAL PRESENTATIONS (10:20 - 12:15)
(Chair: Bill Schertzer)
10:20 - 10:35
Brenda Toth: Closing the Water Balance at the Small Basin Scale.
10:35 - 10:50
Hok Woo and Lawrence Martz: Effects of Sub-grid Variability on the
Water Balance in Mountainous Terrain.
10:50 - 11:15
HEALTH BREAK
11:15 - 11:30
Murray Mackay: The Canadian Regional Climate Model in MAGS.
11:30 - 11:45
Yves Delage: Using an Autonomous 2D Surface Model (CLASS 3.0) as a
Tool to Complete the Surface and Energy Budget at the Surface over the
MAGS Area.
11:45 - 12:00
Kit Szeto: Atmospheric Energy Budget for the MRB from NCEP
Reanalysis Data.
12:00 - 12:05
Ron Stewart: Cloud Water/Ice Content and some NCEP Re-Analysis
Information.
12:05 - 1:30
LUNCH
6
SESSION 2b
INDIVIDUAL PRESENTATIONS (1:30 - 2:40)
(Chair: Kit Szeto)
1:30 - 1:55
Ric Soulis and Geoff Strong: The Mackenzie Water Budget from a
Hydrological Perspective: Progress with WATFLOOD and WATCLASS.
1:55 - 2:10
Wayne Rouse: Energy Balance Data for Tundra, Subarctic Shield and
Subarctic Lakes.
2:10 - 2:25
Bill Schertzer: Energy and Water Exchanges from Large Lakes.
2:25 - 2:40
Werner Wintels and John Gyakum: The Local Diabatic Generation of
Global Available Potential Energy.
2:40 - 3:10
HEALTH BREAK
SESSION 2c
INDIVIDUAL PRESENTATIONS (3:10 - 4:10)
(Chair: Wayne Rouse)
3:10 - 3:25
Henry Leighton: The Solar Radiation Budget of the Mackenzie Basin in
1998-99 and First Estimates of Impacts on the Basin Hydrology.
3:25 - 3:40
Alex Trishchenko: Using Remote Sensing Observations for Mapping
Annual Cycle of Surface Albedo Properties over MAGS Region.
3:40 - 3:55
Anne Walker: Contribution of Satellite-derived Snow Cover and Lake Ice
Information to Understanding the MAGS Energy and Water Cycles.
3:55 - 4:10
Normand Bussières: The CAGES AVHRR Data Base and its Application
to Water Temperature and Cloud Cover Estimation.
TUESDAY, MAY 28
8:45 - 9:25
Coffee, tea or juice
9:25 - 9:30
Plans for the Morning (Geoff Strong)
SESSION 3
BREAKOUT MEETINGS (9:30 - 10:30)
Breakout into two informal groups, one concentrating on the energy budget and the
other on the water budget, to discuss the work that was presented in relation to WEBS
goals and to complete the MAGS-WEBS Progress Chart.
10:30 - 11:00
HEALTH BREAK
7
SESSION 4
WORKSHOP WRAP UP (11:00 - 12:30)
General Discussion Chaired by Ron Stewart and Henry Leighton:
•
•
•
•
12:30 - 1:30
Conclusions from breakout sessions
Where are we now in relation to our goals?
Outstanding Problems
Plans, timelines, publications etc
CLOSING LUNCH
8
APPENDIX II
MAGS WEBS Progress Chart
Model
Space Scale
Time Scale
Obs
Timing
Space Scale
Time Scale
B
Ch
Cq
E
Fro
H
LE
LP
P
Q
RSWsurf
RSWtop
RLWsurf
RLWtop
S
W
Atmos.
Enthalpy Budget
Atmos. Water
Budget
Surface Energy
Balance
Surface Water
Budget
B = heat flux into ground
Cq = convergence of atmospheric total water
Fro = runoff generation
LE = latent heat flux
P = precipitation
RSWsur f= net SW radiation flux at the surface
RLWsurf = net LW radiation flux at the surface
S = sensible heat flux at the surface
Ch = convergence of atmospheric enthalpy
E = evaporation
H = enthalpy
LP = condensation
Q = total atmospheric water content
RSWtop = net SW radiation flux at the top of atmos.
RLWto p= net LW radiation flux at the top of atmos
W = total soil water content
9
Timing
APPENDIX III
WEBS Progress Chart – Water Budget Sub-Group.
Model
Space
Scale
Time
Scale
B
5-15 km
(regional)
Ch
Observations
Timing
Space
Scale
Time
Scale
Timing
100 days
(seasonal)
now
10 km
hourly
now
-
-
-
-
-
-
Cq
15 km
6 hr
now
600 km
lake
12 hr
day, ½ hr
now
now
E
-
-
-
-
-
-
Fro
20 km
hourly
now
river basin
hourly
now
H
-
-
-
-
-
-
LE
-
-
-
-
-
-
LP
15 km
6 hr
now
Sat., acft,
radar
minutes
now
P
15 km
6 hr
now
Stn (50 km)
6 hr –
1 day
now
Q
15 km
6 hr
now
R/S (600
km)
12 hr
now
RSWsurf
-
-
-
-
-
-
RSWtop
-
-
-
-
-
-
RLWsurf
-
-
-
-
-
-
RLWtop
-
-
-
-
-
-
S
-
-
-
-
-
-
W
15 km
hourly
now
basin
points
spring-melt
now
Atmos. Enthalpy Bud.
-
-
-
-
-
-
15 km
6 hr
now
600 km
12 hr
now
Surface Energy Bud.
-
-
-
-
-
-
Surface Water Bud.
20 km
1 hr
now
res. basins
Atmos. Water Bud.
25 km basin
15 km basin
Snow Cover
SWE extent
n/a
daily
now
daily
now
(dashes indicate energy related parameters which are discussed in Appendices IV and V)
10
APPENDIX IV
Inputs to MAGS WEBS Progress Chart* – Energy Budget Sub-Group
* i.e., Appendix II chart
This appendix contains summaries of the information from the various contributors to the Energy
Working Group. In most cases the summaries are highly condensed form documentation
provided by the indicated contributors. The complete text of any section is available from the
contributor or from Henry Leighton. A comprehensive section on the energy budget of lakes
prepared by Schertzer and Binyamin is included in its entirety as Appendix IV.
A. MODEL OUTPUT
Heat Flux into the Ground (Davison)
This part of the energy cycle is modelled in great detail by WATCLASS, taking into account a
variety of land class types, vegetation and snow cover.
Atmospheric Energy Budget Terms (Szeto)
Sources of model output: NCEP I and II reanalyses, NCEP high-resolution regional reanalysis,
CRCM, CMC analysis, ECMWF.
Resolution: NCEP I and II - 2.5 deg lat/lon, 6-hourly; NCEP high-resolution - 32 km; CRCM 50 km, 3 hours (higher temporal resolution possible).
Domain size and archive period: NCEP I and II - global, 1948 - present; ECMWF - global, 1979
- present; NCEP regional analysis - N.America, 1982-2003; CRCM - MAGS simulation
domain, 1993-95 and 1997-99; CMC analysis - depends on model.
Available data and results: NCEP I and II data are readily available. Global budgets from NCEP
I and from ECMWF have been computed by Trenberth. Mackenzie Basin atmospheric
energy budgets extracted from the previously cited NCEP I and ECMWF results by Szeto.
Basin atmospheric enthalpy budgets computed from NCEP I data for the period 1970-2000
by Szeto. Basin atmospheric energy budgets computed from NCEP II by Roads et al. Results
for the Mackenzie Basin from the CRCM are now available for 94-95 and the CAGES water
budget year from Mackay and Szeto. The surface and TOA energy budgets from the CRCM
are not yet complete.
Results to be released in 2002-2003: Budgets from NCEP high-resolution reanalysis; Complete
atmospheric energy budgets from CRCM; CRCM results from longer-term CRCM
simulations.
Evaporation (Davison)
Similar comments as for heat flux into the ground.
11
Albedo and Radiation Fluxes (Szeto and Davison)
Albedo is calculated in WATCLASS for each grid square taking into account the surface types
and presence or absence of snow cover from the various land surface types that are present in
each grid square.
Comments about radiation budgets from atmospheric models are included in the section on
energy budget terms.
Sensible Heat Fluxes (Davison)
Sensible heat fluxes are calculated in WATCLASS for vegetation, bare soil, and snow surfaces
and grid average values are computed.
B. OBSERVATIONS
Heat Flux into the Ground (Woo)
Ground heat fluxes are calculated at meteorological sites from thermal conductivities determined
for different soil types and conditions and measured temperature gradients. Heat flux to snowcover is deduced from surface melt energy which is calculated from the net radiation (measured
directly) and the sensible and latent heat (determined from measurements of wind speed,
temperature and humidity). Measurements are made at Trail Valley (tundra) Wolf Creek
(subarctic woodland slopes and shrub upland) and Carp Lake (Canadian Shield). Data are
obtained at point scales and extrapolated, taking into account land cover, to 10 - 100 m scales, at
one-hour time scales.
Fluxes into lakes are measured at hourly or shorter timescales with vertical lines of
thermocouples suspended in lakes of various sizes near Yellowknife.
The measurements cover the MAGS-1 period and continue in MAGS-2.
Atmospheric Enthalpy Convergence (Gyakum)
Global annual and seasonal maps of the divergence of energy by transient eddies have been
produced by Peixoto and Oort1. A value of 100 W m-2 is a good upper-bound estimate for the
basin average for the period December - February. Values for synoptic-scale and mesoscale
systems may be deduced from rawinsonde data2 or from reanalyses (see the section on models).
For such systems the enthalpy convergence may be of the order of 1300 W m-2 over time scales
of 6 hrs to 2 days and spatial scales of a few hundred km to about 2000 km.
1
2
Piexoto, J.P. and A.H. Oort, Physics of Climate, American inst. Of Physics, 1992, 520pp.
The rawinsonde network over the MRB is too coarse for computation of atmospheric energy budget terms, especially those that
depend on horizontal gradients. Local values of enthalpy, and dry and moist static energy can be computed from rawinsonde
data but for basin-scale budgets reanalysis datasets are probably the most useful, with the rawinsonde data best used for
validation.
12
Convergence of Atmospheric Total Water (Gyakum)
Basin-scale seasonal averages have been computed by Peixoto and Oort1 and are of the order of
1 - 2 cm per month for the latitudes of the Mackenzie Basin. As for enthalpy convergence, total
water convergence associated with synoptic and mesoscale systems can be diagnosed from
rawinsonde data† (see Bosart and Sanders3 and Gyakum and Danielson4). The total water
convergence associated with such systems could reach values as high as 1 - 2 cm per day.
Evaporation and Latent Heat (Woo and Trishchenko)
Surface measurements have been made at meteorological towers in Trail Valley, Wolf Creek and
Carp Lake and from ponds and lakes near Yellowknife. Additional data are available from the
towers erected for the CAGES period. Point data can be extrapolated to scales of 10 to 100 m
depending on the land cover. There is a problem with measurements over steeply sloping terrain.
The point values are useful for comparisons with values deduced from larger scale observations.
The time scale of measurements is 1 hr or less.
CCRS has produced daily ET maps at 1 km resolution from a combination of remote sensing and
modelling and will have 1 km daily lake evaporation by the end of 2002. Historical ET data are
available now; data for recent years will be available by the end of 2002.
Enthalpy Budgets (Szeto)
Basin-scale enthalpy budget, its temporal variability and its relationships to low-frequency
climate variability in the N. Pacific and cold-season temperature extremes over the basin, is
currently being investigated by Szeto with the NCEP data (complete by end of 2002).
Total Condensation (Szeto)
Values are available from MSC monthly averaged precipitation measurements (Hogg and Louie)
and from the NCEP II reanalysis by Roads.
Albedo (Trishchenko)
CCRS will provide narrowband and broadband albedo products at 1 km resolution from multiple
satellite datasets at 10-day intervals. An analytical parameterization of the diurnal variation of
albedo will also be available. Data for recent years will be available at the end of 2002.
There are a limited number of albedo measurements from instrumented towers within the basin.
The representativeness of these measurements depends on the homogeneity of the surface.
Typically the measured albedo is representative of a region with a size of the order of the height
of the radiometers above the surface (metres to a few tens of metres). Accuracy is expected to be
of the order of 5%.
3
4
Bosart, L.F. and F. Sanders, J. Atmos. Sci., 38, 1616-1642, 1977.
Gyakum, J.R. and R.E. Danielson, Mon. WeatherRev.,128, 851-863, 2000.
13
Net Shortwave Flux at the Surface and TOA (Leighton)
Shortwave fluxes at the top of the atmosphere are deduced at 1 km resolution from AVHRR
measurements from the NOAA-12 and NOAA-14 satellites and the times of the satellite
overpasses. Data at other times are interpolated and extrapolated. Monthly averages are
generated over the basin for the CAGES period. Net surface solar radiation is obtained for the
same period from the TOA results by applying the algorithms of Li et al. and Masuda et al.
Shortwave fluxes at the surface are measured from meteorological towers at some of the subbasin experimental sites, from buoys moored in lakes and from a boom suspended over Great
Slave Lake. See the section on measurements over lakes for details.
Longwave Flux at the TOA (Trishchenko and Leighton)
Direct observations of LW TOA flux are currently available from CERES radiometers (20 km
resolution at nadir) onboard the TERRA and AQUA satellites. Calibration stability of these
instruments is better than 0.2%; calibration consistency from ground to space of 0.25%.
Thermal IR window observations by AVHRR (1 km resolution at nadir) could be used to
estimate BB LW observations using NB-BB correlation techniques with an instantaneous
accuracy within 5 to 15 %.
Historical BB data are available from ERBE (40 km resolution at nadir)1984-1989, and ScaRaB
(60 km nadir resolution) 1994-95, 1998-1999 (4 months).
At the present time data from 5 to 6 satellite scenes over the MAGS are available daily but there
are no plans to produce LW TOA flux at daily and sub-daily time scales. Monthly mean data are
available from NASA LARC. Instantaneous fluxes at the times of the satellite passes over the
basin for the four months of CAGES when ScaRaB was operating are archived
Longwave Flux at the Surface (Leighton)
See section on surface-based measurements of shortwave fluxes at the surface.
14
APPENDIX V
The Water and Energy Budgets of Lakes
Components Overview: Measurements, Modelling and Research Gaps
William M. Schertzer
NWRI / CCIW, 867 Lakeshore Rd., Burlington, ON, Canada, L7R 4A6
Contributors:
Wayne R. Rouse, Jacqueline Binyamin, Devon Worth, Claire Oswald,
Peter Blanken and Claude Duguay.
A. OBSERVATIONS
Supporting Meteorological and Limnological Observations over Lakes
Platforms: Meteorological data was measured from 4m Geodyne toroidal meteorological buoys
that contain solar panels for internal operations and batteries and also from Inner Whaleback
Island.
Variables: Meteorological observations recorded at NWRI meteorological buoys included air
temperature and relative humidity (land-based : Vaisala Type HMP35CF; buoy-based Rotronic MP101A), surface temperature (buoys - Stowaway Tidbit; Inner Whaleback Island infrared thermometer (model 4000.GL, Everest Intersciences), and, wind speed (RM-Young
sensor) and wind direction.
Sampling Interval and Recording: Air temperature, relative humidity and surface temperature
were sampled at 2 minute intervals and averaged each 10 minutes. Wind speed and wind
direction were sampled at 6 second intervals and averaged over 10 minutes. All observations
were recorded on Campbell 21x and 23x data loggers at the meteorological buoys.
At Inner Whaleback Island observations were sampled at 2 second intervals, and integrated
over 10 minutes and recorded using a Campbell Scientific CR10x datalogger in 1997 and
1998 and thereafter with Campbell 23x datalogger.
Data Availability: Summer Experiment (1997 - present). Winter experiment (1999/00 - present)
located at Hay River.
Spatial Scale: point measurements; applicable over ~ 103 m2.
Time Scale: 10 minute, hourly and daily averages.
Research Gaps:
• initial comparisons of observed surface water temperature with AVHRR have been
conducted and need to be extended over more years of data.
• initial comparisons of net surface solar radiation from AVHRR algorithms with surface
values have been conducted, verification over additional years of data can be conducted
to quantify the uncertainty.
15
•
•
for application of energy budget models over other parts of the basin and lakes, there
needs to be development of remote sensing algorithms for other variables in addition to
surface temperature and net surface solar radiation (e.g. longwave radiation, air
temperature, relative humidity etc.).
cloudiness is lacking for modelling of some of the radiative flux terms.
Incoming Shortwave Radiation over Great Slave Lake
Instrumentation: Incoming global solar radiation was measured with Eppley pyranometers at all
sites.
Sites: Observations were conducted at 4 locations across Great Slave Lake (Hay River, two
NWRI meteorological buoys and on Inner Whaleback Island).
Sampling Interval and Recording: Observations from the NWRI platforms were sampled at
6 second intervals and totalled every 10 minutes on a Campbell CR23x and Campbell 21x
Datalogger. Instrument calibration is conducted every 2 years at MSC.
At Inner Whaleback Island observations were sampled at 2 second intervals, and integrated
over 10 minutes and recorded using a Campbell Scientific CR10x datalogger in 1997 and
1998 and thereafter with Campbell 23x datalogger.
Data Availability: Summer Experiment (1997 - present). Winter experiment (1999/00 - present)
located at Hay River.
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: 10 minute, hourly and daily averages.
Research Gaps:
• shortwave radiation is observed.
• for extension to other lakes and for years in which there are no observations, solar
radiation needs to be modelled either empirically or radiative transfer scheme, or from
satellite methods.
• for modelling incoming solar radiation, cloudiness is required.
Reflected Solar Radiation from Great Slave Lake
Method: Reflected solar radiation was measured using an inverted Eppley pyranometer.
Sites: Observations were conducted at Inner Whaleback Island in 1997 and 1998 by McMaster
University.
Sampling Interval and Recording: At Inner Whaleback Island observations were sampled at
2 second intervals, and integrated over 10 minutes and recorded using a Campbell Scientific
CR10x datalogger in 1997 and 1998 and thereafter with Campbell 23x datalogger.
16
Data Availability: summer experiment 1997 and 1998 from Inner Whaleback Island.
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: 10 minute, hourly and daily averages.
Research Gaps:
• limited observations.
• largely modelled with a constant albedo.
• need research to determine the seasonal range of albedo for lakes of different sizes over
different latitudes and wave conditions.
• preliminary research has been conducted over some smaller lakes near Great Slave Lake
and also reference to other investigations (i.e. in the Laurentian Great Lakes).
• possibility to incorporate net surface solar radiation (NSSR) from AVHRR into
modelling schemes to approximate albedo or to use NSSR directly - needs to be tested in
energy balance models.
Incoming Longwave Radiation over Great Slave Lake
Instrumentation: Incoming longwave radiation was measured with Eppley Precision Infrared
radiometers (pyrgeometer) and also as a residual in 1997 at Inner Whaleback Island.
Sites: At 3 locations across Great Slave Lake (two NWRI meteorological buoys and on Inner
Whaleback Island).
Sampling Interval and Recording: Observations from the NWRI platforms were read at 6 second
intervals and recorded every 10 minutes on a Campbell 23x Datalogger. Instrument
calibration is conducted every 2 years at MSC.
At Inner Whaleback Island observations were sampled at 2 second intervals, and integrated
over 10 minutes and recorded using a Campbell Scientific CR10x datalogger in 1997 and
1998 and thereafter with Campbell 23x datalogger.
Data Availability: Summer Experiment (1997 - present). Winter experiment (1999/00 - present)
located at Hay River.
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: 10 minute, hourly and daily averages.
Research Gaps:
• longwave radiation is observed.
• for extension to other lakes or for years with no observations, incoming longwave
radiation needs to be modelled.
• for modelling incoming longwave radiation, cloudiness is a major requirement.
17
Net Radiation
Instrumentation: Net radiation was measured from a 14 m boom extended over the water surface
at Inner Whaleback Island using an NR lite net radiometer, made by Kipp and Zonen. In
1999, Q* was not longer directly measured. In year 2002, net radiation is measured using a
Kipp and Zonen CNR1 net radiometer that was used to measure Kdown, and Ldown.
Sites: Inner Whaleback Island, Great Slave Lake.
Sampling Interval and Recording: At Inner Whaleback Island, observations were sampled at
2 second intervals, and integrated over 10 minutes and recorded using a Campbell Scientific
CR10x datalogger in 1997 and 1998 and thereafter with Campbell 23x datalogger.
Data Availability: Summer Experiment (1997 and 1998).
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: hourly and daily averages.
Research Gaps:
• net radiation is observed.
• for modelling, the net radiation is the sum of component values (i.e. solar and longwave
fluxes), however, for the vast number of lakes, these component measurements are not
conducted and support data for modelling individual components over lakes is often not
available.
• need to investigate the possibilities for including remote sensing techniques for either
component radiative fluxes or the net radiation over various surface types (e.g. lakes).
Attenuation of Solar Radiation in the Water Column
Instrumentation: Secchi disk and transmissometer.
Sites: at 5 locations in Great Slave Lake and also at selected smaller lakes near Great Slave Lake.
Sampling Interval and Recording: Few point observations on Great Slave Lake and also at some
smaller lakes.
Data Availability: Summer Experiment (1998 - present) at time of mooring deployments and
retrievals.
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: ~ daily to weekly and seasonal average?
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Research Gaps:
• the attenuation coefficient (Beer's Law) is important in thermal modelling of lakes.
• only very few observations in Great Slave Lake and in the smaller lakes.
• little information on the spatial variability of the mean vertical light extinction coefficient
from measurements.
• little supporting data for modelling of this component and as a consequence only an
approximate value can be incorporated within the lake thermal models.
Lake Ice Cover Duration (Freeze-up & Break-up dates)
Instrumentation: Passive microwave SSM/I data.
Sites: Great Slave Lake.
Sampling Interval and Recording: Several 12.5-25 km pixels acquired twice daily.
Data Availability: 1988 to 1999. (Anne Walker)
Spatial Scale: 12.5 km pixels (SSM/I 85 GHz).
Time Scale: Twice daily (morning and afternoon overpasses).
Research Gaps:
• coarse resolution of pixels limits the use of SSM/I data to very large lakes (Great Slave,
Great Bear, and Athabaska to some extent).
• freeze-up and break-up dates may be derived using ice cover observations made
operationally by the Canadian Ice Service (CIS) with Radarsat and NOAA AVHRR. The
temporal scale is 1 week.
• need more research in the development of methods for deriving freeze-up and break-up
dates, and consequently the ice-free period, using data from new satellite missions (e.g.
MODIS on Terra and Aqua, AMSR on Aqua, ASAR and AATSR on Envisat). Freeze-up
and break-up dates will be determined with an accuracy of 1-2 days.
B. MODELLING
Emitted Longwave Radiation from Great Slave Lake
Method: Emitted longwave radiation is a computed value based on surface temperature.
Sites: Emitted longwave was computed over six sites in Great Slave Lake based on surface
temperature observations from lake buoys and also based on infrared thermometer on Inner
Whaleback Island.
Sampling Interval and Recording: Surface temperature was sampled at 2 minute intervals and
averaged each 10 minutes.
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Data Availability: Summer Experiment (1997 - present).
Spatial Scale: point measurement; applicable over ~ 103 m2.
Time Scale: 10 minute, hourly and daily averages.
Research Gaps:
• longwave radiation is a computed value based on surface water temperature.
• surface water temperature measurements are not "skin" temperature.
• need more research to refine derivation of surface temperatures from AVHRR for large
lakes.
• need more research to test application of AVHRR algorithms over a range of lakes.
• need to determine the accuracy of using AVHRR derived temperatures in the emitted
longwave computation for lakes of different sizes.
• need to incorporate weather variability in the existing AVHRR quadratic functions for
water surface temperature.
• need to model emitted longwave radiation over other lakes in the MAGS basin.
Latent Heat Flux fom Lakes
Method: Eddy correlation at Inner Whaleback Island and by mass transfer technique at the
meteorological buoys.
Sites: 5 sites across Great Slave Lake.
Data Requirements: The mass transfer technique requires observations of air temperature,
relative humidity, wind speed and surface water temperature. These meteorological
components were sampled and recorded at each site (see Supporting Meteorological and
Limnological Observations above).
Results Availability: ice-free periods in 1997 – present.
Spatial Scale: data from a point; extended over ~ 103 m2.
Time Scale: hourly and daily.
Research Gaps:
• extension of modelling at sites to the entire lake.
Sensible Heat Flux from Lakes
Method: Eddy correlation at Inner Whaleback Island and application of Bowen's ratio at
meteorological buoys.
Sites: 5 sites across Great Slave Lake.
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Data Requirements: The mass transfer technique requires observations of air temperature,
relative humidity, wind speed and surface water temperature. These meteorological
components were sampled and recorded at each site (see Supporting Meteorological and
Limnological Observations above).
Results Availability: ice-free periods in 1997-present.
Spatial Scale: data from a point; extended over ~ 103 m2.
Time Scale: hourly and daily.
Research Gaps:
• extension of modelling at sites to the entire lake.
Lake Evaporation
Method: Eddy correlation at Inner Whaleback Island and application of Bowen's ratio at
meteorological buoys.
Sites: 5 sites across Great Slave Lake.
Data Requirements: The mass transfer technique requires observations of air temperature,
relative humidity, wind speed and surface water temperature. These meteorological
components were sampled and recorded at each site (see Supporting Meteorological and
Limnological Observations above).
Results Availability: ice-free periods, 1997-present.
Spatial Scale: data from a point; extended over ~ 103 m2.
Time Scale: hourly and daily.
Research Gaps:
• extension of modelling at sites to the entire lake.
• comparison of evaporation derived from other techniques (e.g. eddy correlation, mass
transfer, aerodynamic, energy budget, combination methods and water budget).
Condensation at the Lake Surface
Method: Eddy correlation at Inner Whaleback Island and application of Bowen's ratio at
meteorological buoys.
Sites: 5 sites across Great Slave Lake.
Data Requirements: The mass transfer technique requires observations of air temperature,
relative humidity, wind speed and surface water temperature. These meteorological
21
components were sampled and recorded at each site (see Supporting Meteorological and
Limnological Observations above).
Results Availability: ice-free periods.
Spatial Scale: data from a point; extended over ~ 103 m2.
Time Scale: hourly and daily.
Research Gaps:
• extension of modelling at sites to the entire lake.
Thermal Modelling of Lakes (also link and coupled lake-atmosphere models)
Model Approaches: 0-dimension
(hydrodynamic model).
(whole
lake);
1-dimension
(vertical);
3-dimension
Database: Meteorology, radiation and turbulent exchanges for 1997-present in Great Slave
Lake; also data for small lakes. Vertical temperature profiles for model development and
verification.
Research Gaps:
• initial implementation of thermal modelling has started on Great Slave Lake and smaller
lakes.
• require inter-comparison of thermal models and ice sub-models.
• require collaboration with remote sensing of radiation (AVHRR), surface temperature
(AVHRR), ice break-up and freeze-up (SSM/I), remote sensing of cloudiness.
• research on the modelling accuracy on a sample of lakes of different sizes.
• research on methodologies to extend research over lakes within the MAGS basin.
• research to link and couple lake-atmosphere models.
Lake Ice Cover Duration
Method: 1-dimensional (vertical) thermodynamic lake ice model.
Sites: Great Slave Lake (2 sites in bays; 1 site near the mouth of Hay River; central section of
GSL).
Data Requirements: The 1-D model requires observations of air temperature, relative humidity,
wind speed, cloud cover, and snowfall. These meteorological components are measured at
MSC weather stations.
Results Availability: 1961-2000.
Spatial Scale: data from a point; extended over the central section of GSL.
22
Time Scale: hourly and daily (model has only been used with daily time steps to date).
Research Gaps:
• require improvement of the treatment of snow cover.
• research on the modelling accuracy on a sample of lakes of different sizes.
• need to compare parameters of the radiation and energy budget generated by the model
(year-round) with observations from meteorological stations and satellites.
Additional Contribution by Jacqueline Binyamin
The latent (LE) and sensible (S) heat fluxes are directly measured with the MK2 Hydra eddy
covariance system during open water periods at Great Slave Lake (GSL) and other small lakes
(e.g. Sleepy Dragon, Skeeter Lake and Gar Lake). The hydra system underestimates flux
measurements by 3%.
Space scale: 5-8 km. Time scale: 1/2 hourly values. Timing: 1997-2001 (5 years) for GSL and
2000 (one year) for other small lakes. Limitation: these measurements may not be representative
of LE and S from the entire GSL. Also measurements are only available for the open water
periods.
In addition to in-situ observations, LE and S can be estimated from satellite data.
Space scale: global. Grid (Lat. x Log.) 4 x 5 degrees and 2.0 x 2.5 degrees.
Time scale: one day or every 6 hours. Timing: 1/1/1979-12/31/88.
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APPENDIX VI
List of Participants – MAGS WEBS Workshop
Name
Affiliation
E-mail Address
Binyamin, Jacqueline
Bobba, A. Ghosh
Bussieres, Normand
Crawford, Bob
Davison, Bruce
Delage, Yves
Derksen, Chris
di Cenzo, Peter
Gyakum, John
Leighton, Henry
Liu, Jinliang (John)
Louie, Paul
Mackay, Murray
Martz, Lawrence
Reuter, Gerhard
Rouse, Wayne
Schertzer, Bill
Seglenieks, Frank
Soulis, Ric
Stewart, Ron
Strong, Geoff
Szeto, Kit
Toth, Brenda
Trischenko, Alexander
Verseghy, Diana
Walker, Anne
Wang, ShuSen
Woo, Hok
McMaster University
NWRI-Burlington
MSC-Downsview
MSC-Downsview
University of Waterloo
MSC-Dorval
MSC-Downsview
NHRC
McGill University
McGill University
MSC-Downsview
MSC-Downsview
MSC-Downsview
University of Saskatchewan
University of Alberta
McMaster
NWRI-Burlington
University of Waterloo
University of Waterloo
MSC-Downsview
Consultant
MSC-Downsview
NWRI-Saskatoon
CCRS
MSC-Downsview
MSC-Downsview
CCRS
McMaster University
binyamj@mcmaster.ca
Ghosh.Bobba@ec.gc.ca
Normand.Bussieres@ec.gc.ca
Robert.Crawford@ec.gc.ca
bjdaviso@uwaterloo.ca
Yves.Delage@ec.gc.ca
Chris.Derksen@ec.gc.ca
Gewex.Mags@ec.gc.ca
gyakum@zephyr.meteo.mcgill.ca
Henry.Leighton@mcgill.ca
Jinliang.Liu@ec.gc.ca
Paul.Louie@ec.gc.ca
Murray.Mackay@ec.gc.ca
lawrence.martz@usask.ca
Gerhard.Reuter@ualberta.ca
Rouse@mcmaster.ca
William.Schertzer@ec.gc.ca
frseglen@waterloo.ca
rsoulis@uwaterloo.ca
Ron.Stewart@ec.gc.ca
geoff.strong@shaw.ca
Kit.Szeto@ec.gc.ca
Brenda.Toth@ec.gc.ca
trichtch@ccrs.nrcan.gc.ca
Diana.Verseghy@ec.gc.ca
Anne.Walker@ec.gc.ca
Shusen.Wang@ccrs.nrcan.gc.ca
woo@mcmaster.ca
24