Weather & Climate of Virginia Robert E. Davis Professor of Climatology Dept. of Environmental Sciences University of Virginia Email: red3u@virginia.edu Rivanna Master Naturalists March 14, 2017
Arctic Circle Tropic of Cancer
SEASONS
Effect of Solar Angle
circle of illumination Radiation receipt: 1) sun angle (intensity) 2) day length (duration)
Top of Atmosphere Sunlight Arctic 0 44 Charlottesville 16 41 Equator 34 36
Continentality Mean temperature of warmest minus coldest month
Incoming Outgoing
General Circulation of the Atmosphere
Ocean Circulation
Jet Stream: 1) Boundary between warm, tropical and cold, polar air masses cold 2) Size and strength vary seasonally 3) Linked to midlatitude storms at surface warm 4) Linked to storm tracks 5) A component of (circum)-polar vortex
Jet Stream (Polar Vortex) Patterns
JANUARY JULY COLD! COOL IN WINTER, JET STREAM 1) EXPANDS 2) STRENGTHENS http://www.classzone.com/books/ earth_science/terc/content/ investigations/es1906/ es1906page02.cfm
A (Very) Short Course on Weather
Storms are low pressure systems
L! Types of Fronts
Cold Front (vertical cross-section)
Warm Front (vertical cross-section)
Cold Air Warm Air
Average January Winds North wind Richmond Southwest wind (color = speed)
Average July Winds North wind Richmond (color = speed)
July Mean Maximum Dew Point Temperature
Common Wind Directions Aloft Surface
Rain Shadow Effect
Mountain Effects (Elevation: 1000 feet) (Elevation: 3500 feet)
Charlottesville Precipitation thunderstorms hurricanes fronts
SUMMER
% Rainfall (May-Nov) from Tropical Cyclones Knight and Davis, 2007
Charlottesville Climatic Water Budget AE = Actual Evapotranspiration PE = Potential Evapotranspiration P = Precipitation millimeters
P PE Surplus
PE Deficit P
PHENOLOGY Study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life
PHRENOLOGY Study of the and size of the cranium as a (supposed) indication of character and mental abilities
Grape Phenology Light, heat accumulation, soil moisture
Organism Growth and Temperature growth begins growth at maximum
Growing Degree Days (GDDs) accumulated degrees over time above a baseline and below a maximum, based on daily mean temperature April 10: Max = 65, Min = 45, so Mean = 55; 55 50 = 5 GDDs April 11: Max = 70, Min = 50, so Mean = 60; 60 50 = 10 GDDs Season total = 15 GDDs
Growing Degree Days (GDDs) These vary by organism! corn baseline = 50 F lettuce baseline = 42 F potato baseline = 46 F
Growing Degree Days (GDDs) As of Sunday (3/12), CHO had accumulated 200 (corn) GDDs 140 above average for that date Cautions Some organisms are more light than heat sensitive, so GDDs will not be as useful Proper growth depends on adequate soil moisture as well as heat accumulation
Average Accumulated GDDs for Mar. 12
2017 Accumulated GDDs for Mar. 12
GDDs to Date Average http://pnwpest.org/se/ddmaps.html 2017
Plant Hardiness Zones Average of each year s lowest minimum temperature
Plant Hardiness Zones http://planthardiness.ars.usda.gov/phzmweb/interactivemap.aspx
Hardiness Zone Changes
Average Date of Last Spring Frost Freeze Frost 6-Apr 17-Apr 22-Apr 6-May 23-Apr 5-May 6-May 17-May 25-Apr 11-May 27-Apr 8-May 6-May 18-May 2-May 17-May???????? 90 th percentile
Average Date of Last Spring and First Fall Frost Continental U.S. 6 4 Later Earlier Deviation from average (days) 2 0-2 -4 Long-term average Fall frost Spring frost -6 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year (Kunkel, 2009)
Length of Growing Season, 1900 2002 Continental U.S. 15 Deviation from average (days) 10 5 0-5 Long-term average -10 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year (Kunkel, 2009)
Virginia Annual Temperatures 1898 2016 58 Virginia Statewide Annual Temperature Temperature ( F) 56 54 52 1900 1950 2000 Year
Virginia Annual Precipitation: 1898 2016
Weather & Climate of Virginia Robert E. Davis Professor of Climatology Dept. of Environmental Sciences University of Virginia Email: red3u@virginia.edu Rivanna Master Naturalists March 14, 2017
Here are some websites related to my presentation that might be of interest: Jet stream animation http://www.classzone.com/books/earth_science/terc/content/ investigations/es1906/es1906page02.cfm Plant Hardiness maps http://planthardiness.ars.usda.gov/phzmweb/interactivemap.aspx Animation of current global winds, ocean currents, etc. http://earth.nullschool.net/#current/wind/isobaric/250hpa/ orthographic=-43.14,8.77,356