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Climate Projection Data Statement

This page is part of the project: Apostle Islands

Future Climate Projection Data Statement

Global Climate Models (GCMs) are used to generate future climate data that are often used in climate adaptation planning efforts.  Dozens of GCMs exist as modeling groups try to improve the representation of important physical processes such as precipitation, sea ice, ocean circulation, etc.  Because GCMs are global in nature—simulating climate dynamics over the entire earth—they do not necessarily capture regional and local climate dynamics well.  The Great Lakes and their impact on regional climate are very important locally, but they are typically not represented with much detail in GCMs.  Hence, finer spatial resolution climate models, called Regional Climate Models (RCMs), were developed to simulate smaller regions on the globe with better fidelity.  RCMs are responsible for simulations within a specified geographic region (i.e., the Great Lakes), and GCMs supply the climate conditions at the boundary of that region.

In this project we will be relying on a set of dynamically downscaled (RCM-based) climate projections designed for the Great Lakes region.  The RCM employed offers reasonably good representations of regional air temperatures, precipitation, lake ice, lake-effect snowfall and captures the seasonal cycle of temperature differences between the lake surface and overlying air (a factor of regional atmospheric stability) (Notaro et al 2013).  All of these components contribute to the credibility of the data.  These data were produced by the Nelson Institute Center for Climatic Research at the University of Wisconsin-Madison.  One RCM is used in combination with six different GCMs, which supply the boundary conditions, producing six different representations of the future climate for each variable (see list below).  Data for two future periods are available, mid- and late-21st century. 

Link to Data: http://nelson.wisc.edu/ccr/resources/dynamical-downscaling/index.php

Available Climate Variables

Temperature
Average daily temperature (degrees Fahrenheit).

Precipitation
Average seasonal or annual precipitation in inches.

Maximum Temperature
Average daily high temperature (degrees Fahrenheit), based on hourly data.

Minimum Temperature
Average daily low temperature (degrees Fahrenheit), based on hourly data.

Diurnal Temperature Range
Average diurnal temperature range (degrees Fahrenheit), computed by substracting the average daily low temperature from the average daily high temperature.

Growing Season Length
Average growing season length, computed as the mean number of days between the last spring freeze and first autumn freeze, where a freeze is when the daily low temperature drops below 32°F.

Date of First Fall Freeze
First fall freeze, defined as the first day, after mid-summer, with a low temperature below 32°F.

Date of Last Spring Freeze
Last spring freeze, defined as the last day, between January 1 and mid-summer, with a low temperature below 32°F.

Growing degree days
Growing degree days (GDDs) for a single day are computed here as the number of degrees Fahrenheit that the daily mean temperature exceeds 50°F. So, two d ays with daily mean temperatures of 75°F and 40°F have 25 and 0 GDDs, respectively. For annual total GDDs, the GDDs for each day are summed.

Freezing degree days
Freezing degree days (FDDs) for a single day are computed here as the number of degrees Fahrenheit that the daily mean temperature is below 32°F. So, two days with daily mean temperatures of 20°F and 40°F have 12 and 0 FDDs, respectively. For annual total FDDs, the FDDs for each day are summed.

Cooling degree days
Cooling degree days (CDDs) for a single day are computed here as the number of degrees Fahrenheit that the daily mean temperature exceeds 65°F. So, two days with daily mean temperatures of 75°F and 50°F have 10 and 0 CDDs, respectively. For annual total CDDs, the CDDs for each day are summed.

Heating degree days
Heating degree days (HDDs) for a single day are computed here as the number of degrees Fahrenheit that the daily mean temperature is below 65°F. So, two days with daily mean temperatures of 50°F and 75°F have 15 and 0 HDDs, respectively. For annual total HDDs, the HDDs for each day are summed.

Nights Below 0F
Cold Nights: Mean number of nights each year with a low temperature below 0F.

Days Below 20F
Cold Days: Mean number of days each year with a high temperature below 20F.

Days Above 90F
Hot Days: Mean number of days each year with a high temperature above 90F.

Days Above 100F
Hot Days: Mean number of days each year with a high temperature above 100F.

Days With Precipitation
Mean number of days per year with precipitation of at least 1 mm.

Frequency of 1" precipitation events
Frequency of 1" precipitation events, defined here as the number of days per decade with precipitation of at least one inch.

Frequency of 2" precipitation events
Frequency of 2" precipitation events, defined here as the number of days per decade with precipitation of at least two inches.

Frequency of 3" precipitation events
Frequency of 3" precipitation events, defined here as the number of days per decade with precipitation of at least three inches.

Sea-Level Pressure
Average sea-level pressure in hPa (mb).

Near Surface Specific Humidity
Average near-surface specific humidity in g/kg.

Evapotranspiration
Average actual total evapotranspiration (inches/year or inches/season).

Cloud Cover Fraction
Average cloud cover fraction (fraction).

Duration of Sunshine
Mean length of daily sunshine in seconds.

Upper Soil Moisture
Mean upper soil moisture fraction in kg/m2.

Lower Soil Moisture
Mean lower soil moisture fraction in kg/m2.

Snowfall
Annual mean snowfall (top - cm, bottom - %).

Liquid Snow Depth
Mean November-April liquid-equivalent snow depth (top - kg/m2, bottom - %).

Days With Snowfall
Mean number of days per year with a snowfall of at least 1 cm (top - days, bottom - %).

References

Notaro, Michael, et al. "Influence of the Laurentian Great Lakes on Regional Climate." JOURNAL OF CLIMATE. 26 (2013): 789-804.