State Climatologist Office for Maryland
Final Report FY2011
To the Maryland Department of the Environment
Konstantin Vinnikov, Acting State Climatologist for Maryland
Russell R. Dickerson, Professor
Department of Atmospheric Science, University of Maryland
Abstract
This year’s activity by the State climatologist office for Maryland included routine climate
service coupled with monitoring and interpretation of observed regional climate change. We
showed that century-scale change of MD climate follows the classic greenhouse global warming
scenario with cold season amplification of temperature and a noticeable increase in annual
precipitation. We found that summer time precipitation has a tendency to decrease in all eight
climate divisions of MD. Potential consequences of this decrease in summer precipitation
together with increase in temperature should be evaluated. More surprising preliminary results
show that there is no noticeable or statistically significant increasing trend in the annual number
of days with temperatures above 100 F.
Climate Service: Summary of Activities in 2011
The office of the State Climatologist of Maryland is the center for analysis, interpretation
and distribution of climactic information for the State of Maryland. Climate data is provided to
governmental agencies, businesses, students, researchers, and citizens of Maryland. We
maintain links with many cooperative meteorological stations in the state, as well as the National
Climactic Data Center, the National Weather Service Forecasting Office, and the National
Oceanic and Atmospheric Administration.
The office of the State Climatologist of Maryland received more than 100 data requests in
2011. Nearly all data requests were handled by accessing the data from the National Climatic
Data Center, and forwarding the data to the recipient in accordance to the requesters’
preferences. The majority of data requests were of precipitation or temperature data for a
specific location and timeframe. Specifically, lawyer and attorney offices would request weather
reports for a certain day and time for a specific location (i.e. street or intersection) as the nature
of their claims needed that type of detail. Many other requests were received from students,
researchers, and employees of governmental agencies such as wind histories (gusts and
direction), seasonal outlooks (spring and summer climate outlook), or hydrological outlooks
(drought conditions). This past year, we have been contacted with requests from students
attending the University of Maryland, Hood College, the United States Naval Academy, and
Pennsylvania State University. Some government agencies that have requested data include the
Maryland Department of the Environment, National Plant Materials Center, Naval Research Lab,
USEPA Office of Research and Development - National Risk Management and Research
Laboratory, Maryland Department of Natural Resources, and the Department of the Army as part
of the Critical Infrastructure Risk Management (CIRM) program. Businesses have contacted the
office for climate data for projects they are working on. In general, most requests are handled
with data from the National Climactic Data Center. Data from Maryland COOP stations has
been used in data requests along with data from the National Weather Service Forecasting
Office. One other main type of request we have received has been from local media outlets, such
as radio stations, local newspapers, etc. asking for an interview or statement about climate
conditions. To mention a few: WBAL Radio News, Midday with Dan Rodricks 88.1 WYPR,
The Baltimore Sun, and The Queen Anne's Chronicle. The Office of the State Climatologist also
works with Maryland COOP stations. We receive and archive monthly climate data records
from approximately thirty sites from all over the state of Maryland. These COOP stations are
managed and operated by private citizens. Some of the data requests require special research.
They are mostly related to information on regional climate change for monitoring and managing
natural resources and climate dependent entrepreneurial activities. Few examples are below.
Observed century scale climatic trends in temperature and precipitation
Recent revolution in the NCDC/NOAA approach to homogenization of historical longterm climatic records created many problems for climate services. New data, that should be
used, are often not yet officially released. Old data, which should not be recommended for use
anymore, is still available from the official NCDC web site. Obtaining the proper version of data
is currently possible through direct contact with NCDC scientists only. The time series of state
and climate division averages of monthly temperatures are most often used to evaluate regional
climatic trends. As an example Figures 1-5 display a map of MD climate divisions, seasonal
variations of means, standard deviations, and linear trends of temperature and precipitation for
the period of observation from 1895.
Figure 1. Schematic map of the NOAA climate divisions for Maryland: 1-Southeastern Shore;
2-Central Eastern Shore; 3-Lower Southern; 4-Upper Southern; 5-Northeastern Shore; 6-North
Central; 7-Appalachian Mountains; 8-Allegheny Plateau.
These estimates are based on the US Historical Climate Network v.2 monthly
temperature and precipitation data set. Averages for MD Climate Divisions are obtained by Dr.
Russell Vose (NCDC/NOAA). The estimates show that climate of MD is warming and follows
the winter amplification scenario. Cold season temperature is rising faster compared to warm
season temperature (Figure 5.2). Summer warming is rather weak almost everywhere in MD and
is about 1°F/100 yr. Such a low rate of seasonal warming is not really detectable or statistically
significant in regional climatic records. Nevertheless, this almost negligible warming is
accompanied by a decrease in summer precipitation. This decrease is compensated by increased
precipitation in other seasons (spring and autumn) and may cause many environmental and
economical consequences for citizens of MD. These include decrease of summer water
resources, increase in occurrences of severe droughts, increase in accumulation of dry biomass in
the not well-managed forests.
Figure 2. Seasonal variations of 1895-2012 means and standard deviations of monthly
temperature in the MD climate divisions.
Figure 3. Seasonal variations of 1895-2012 linear trends of temperature in the MD climate
divisions.
Figure 4. Seasonal variations of 1895-2012 means and standard deviations of monthly
precipitation in the MD climate divisions.
Figure 5. Seasonal variations of 1895-2012 linear trends of temperature in the MD climate
divisions.
Observed century-scale climatic trend in occurrence of heat waves
The more complicated question is about climatic trends in occurrence of heat waves. The
problem is that century-scale climatic records in Maryland do not provide the full information
needed for recognition of heat waves. In addition, available records are not homogeneous.
Practically, only the daily maximum temperature observations can be used for heat wave
recognition. Let us simplify heat wave definition and assume that a day with Tmax≥100°F is a
heat wave day. Figure 6 displays preliminary results just for one station, Laurel, MD. Raw, but
quality controlled daily data on Tmax has been used to compute a time series of the annual
number of days with Tmax above the thresholds 90, 95, and 100°F. We then used ordinary least
squares technique to obtain linear trend estimates.
Figure 6. Laurel, MD. Time series of annual number of days with Tmax≥90, 95, 100 F/year and
their linear trends.
These preliminary estimates show that the number of days with maximum temperature exceeding
90 and 95°F have been increasing with rate 7.6±4.2 and 4.2 ±2.3 days per century. This is quite
consistent with summer warming trend in the MD Upper Southern climate division, which is
about 2°F/century (Figure 3). More surprising is that there is no noticeable and statistically
significant trend in the number of days with temperature above 100°F. This means that increase
in mean temperature at this station is accompanied by decrease of its variability. At this stage of
study we see no observational evidence of increase in the occurrence of heat waves in this
climatic record. This work should be continued.