Precip. References: Jennifer Francis
Fxrland, E.J. and I. Hanssen-Bauer, 2000: Increased Precipitation in the Norwegian
Arctic: True or False? Climatic Change, 46, DOI:
10.1023/A:1005613304674.
Abstract: Results from the WMO Solid Precipitation MeasurementIntercomparison and
parallel precipitationmeasurements from Svalbard are used to evaluate andadjust models
for estimating true precipitation underArctic conditions. The conclusion is that
trueprecipitation in the Arctic may be estimatedreasonably well when the wind speed at
gauge height isless than 7 m/s. It is possible to give good estimatesof true annual and
seasonal precipitation at Svalbard,as only a small part of the precipitation is fallingat
wind speeds above 7 m/s. For rough calculations,the correction factors for liquid
precipitation isestimated to be 1.15 and for solid precipitation1.85.The developed
correction models are used to estimateamounts and trends of true precipitation for two
sitesin the Norwegian Arctic. In Ny-Elesund the trueannual precipitation is more than
50% higher than themeasured amount. As the aerodynamic effects leading toprecipitation
undercatch are dependent onprecipitation type and temperature, the observed
andprojected increase in the air temperature in theArctic would also affect the measured
precipitation,even if the true precipitation was unchanged. Sincethe mid 1960s the
temperature at Svalbard Airport hasincreased by 0.5 0C per decade, resulting in areduced
fraction of annual precipitation falling assnow. In the same period, the measured
precipitationhas increased by 2.9% per decade and the `true' by1.7% per decade.
Estimates are made of the fictitiousprecipitation increase that would result from ageneral
temperature increase of 2, 4 and 6 0C. The increase in the measured annual
precipitationwould be 6, 10 and 13%, respectively. The expectedfictitious precipitation
increase is thus of the samemagnitude as the real precipitation increase whichaccording to
recent GCM projections may be expected inNorthern Europe as a result of a doubling of
theatmospheric CO2 content.
-------------------------------------------------------------Lambert, F.H., P.A. Stott, M.R. Allen, and M.A. Palmer, 2004:
Detection and attribution of changes in 20th century land precipitation, Geophys. Res.
Lett., 31, L10203, doi:10l1029/2004GL019545.
Abstract: Observed globally-averaged land precipitation changes over the 20th century
are compared with simulations of the HadCM3 climate model using an ``optimal
fingerprinting'' method. We find that observed changes in precipitation are too large to be
consistent with model-generated internal variability and are consistent with (attributable
to) the combination of natural and anthropogenic forcings applied to the model. By
comparing precipitation observations to shortwave and longwave forcing timeseries, we
find that most of the forced variation in precipitation appears to be driven by natural
shortwave forcings. We are unable to detect a response to anthropogenic longwave
forcings in isolation. Finally, we seek to explain these results in terms of perturbations to
the energy budget of the troposphere.
----------------------------------------------------Peterson, B.G., R.M. Holmes, J.W. McClelland, C.J. Vorosmarty, R.B.
Lammers, A.I. Shiklomanov, I.A. Shiknomanov, and S. Rahmstorf, 2002:
Increasing river discharge to the Arctic Ocean, Science, 298, 2171-2173.
Abstract: Synthesis of river-monitoring data reveals that the average annual discharge of
fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from
1936 to 1999. The average annual rate of increase was 2.0 1 0.7 cubic kilometers per
year.
Consequently, average annual discharge from the six rivers is now about 128 cubic
kilometers per year greater than it was when routine measurements of discharge began.
Discharge was correlated with changes in both the North Atlantic Oscillation and global
mean surface air temperature. The observed large-scale change in freshwater flux has
potentially important implications for ocean circulation and climate.
-------------------------------------------------------------Groves, D.G. and J.A. Francis, 2002: Moisture budget of the Arctic atmosphere from
TOVS satellite data, J. Geophys. Res., 107, 4391, doi:10.1029/2001JD001191.
Abstract: The Arctic atmospheric moisture budget is an important component of the
Arctic climate system, and moisture transport is a major mechanism by which both local
and hemispheric atmospheric processes affect the Arctic Ocean. The lack of humidity
data over the Arctic Ocean severely hampers present understanding of climatological and
time-varying features of the Arctic moisture budget. We combine daily satellite
precipitable water retrievals from the NASA/NOAA TIROS Operational Vertical
Sounder (TOVS) Polar Pathfinder data set with wind fields from the NCEP-NCAR
Reanalysis to create a new high-resolution data set of the Arctic atmospheric moisture
budget from October 1979 to December 1998. Products are at a horizontal resolution of
(100 km)2 and include daily fields of precipitable water and precipitable water flux
profiles at 16 vertical levels and net precipitation (i.e., precipitation minus evaporation, PE). We show that these retrievals compare well with rawinsonde-derived moisture
transport and reanalysis products, yet capture spatial and temporal variability that other
data sets cannot owing to the sparse coverage of the conventional observation network in
the Arctic Ocean.
Our method yields an average annual net precipitation of 15.1 cm
yr−1 over the polar cap (poleward of 700N) and 12.9 cm
yr−1 over the Arctic Basin. Poleward moisture transport into the Arctic is greatest
from June to August and smallest in December.
Over regions of known storm tracks, especially in the North Atlantic sector, we find that
transient circulation features account for 32% of the net precipitation in the GreenlandIceland-Norwegian Seas, 90% in the Nansen Basin, and 74% in the Arctic basin as a
whole.
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Groves, D.G. and J.A. Francis, 2002: Variability of the Arctic atmospheric moisture
budget from TOVS satellite data, J. Geophys.
Res., 107, 4785, DOI 10.1029/2002JD002285.
Abstract: Temporal and spatial variability of the Arctic atmospheric moisture budget is
investigated using a new 19-year data set (1980 to
1998) produced from daily precipitable water retrieved from the TIROS Operational
Vertical Sounder (TOVS) and upper-level winds from the NCEP-NCAR Reanalysis. A
companion paper describes the creation and validation of these new moisture budget
products [Groves and Francis, 2002]. Seasonal differences in moisture transport arise
from distinct winter/summer circulation regimes and meridional moisture gradients.
In winter, approximately 80% of the net precipitation (precipitation minus evaporation,
P-E) is transported along well-defined storm tracks. Summer P-E is double that of winter
and dominates the annual pattern. Decadal differences in winter P-E reveal statistically
significant increases in the Beaufort and eastern Greenland-Iceland-Norwegian Seas,
decreases in the Canadian Archipelago (islands in far northeast Canada) and Kara Sea,
and a slight increase in the Arctic as a whole. Annual differences are dominated by winter
changes. When the phase of the Arctic Oscillation
(AO) index is positive, the net PW flux across 700N in winter is 6 times larger than on
negative-index days. Over the entire Arctic, P-E is 29% larger (20% lower) than the
average on days with a positive
(negative) AO index. In summer the PW transport is twice as large, and P-E is 27%
higher on positive versus negative AO days. These results suggest that if the AO
continues its trend toward a predominantly positive phase, we should expect to observe
increasing precipitation in the Arctic overall, and particularly in regions adjacent to the
marginal ice zones.