Rogue Valley Weather and Climate Modified from program by Gregory V. Jones, Southern Oregon University
Talk Outline General Weather and Climate Overview Weather and Climate Large Scale Controls Weather and Climate Local to Site Controls Overview of Climate-Soil-Water Relationships Overview of Climate Zoning for Plants Guidelines for Realizing Gardening Potential Weather and Climate Resources
WEATHER & CLIMATE Individual Weather Events Climate Variability Climate Change
Climate Solar Radiation Temperature Frost Avoidance and Cold Air Drainage Water Wind
Scales of Climatic Effects Macroscale Mesoscale Microscale
WEATHER & CLIMATE Controls There are seven general controls 1) LATITUDE 2) DISTRIBUTION OF LAND & WATER 3) GENERAL CIRCULATION OF THE ATMOSPHERE 4) GENERAL CIRCULATION OF THE OCEANS 5) ELEVATION 6) TOPOGRAPHIC BARRIERS 7) STORMS
WEATHER & CLIMATE Controls 1) LATITUDE: the most basic of controls. The rotation of the earth on its axis and its revolution around the sun alter solar radiation receipt across the surface. Controls mostly temperature due to variations in incoming solar radiation
Mild Midlatitude Climates (Zone C) Mediterranean dry, hot or warm summer Marine West Coast less of a dry season, warm or cool summer
WEATHER & CLIMATE Controls 2) DISTRIBUTION OF LAND & WATER: Oceans and other bodies of water heat & cool more slowly and to a lesser degree. Additionally, the high moisture source moderates climates controls mostly moisture and temperature variations.
Example of Temperature Changes from the Coast in California
WEATHER & CLIMATE Controls 3) GENERAL CIRCULATION OF THE ATMOSPHERE The constant motion of the air controls moisture and storminess.
AIR MASSES: Air masses are large bodies of air with uniform conditions of temperature, humidity and stability Major classes include: Arctic, Polar, Tropical, and Equatorial and whether the air is maritime or continental.
WEATHER & CLIMATE Controls 4) GENERAL CIRCULATION OF THE OCEANS: Very similar to the motions in the atmosphere because ocean circulation patterns are driven by the winds. Controls mostly moisture.
WEATHER & CLIMATE Controls 5) ELEVATION: changes in altitude exert strong controls on pressure, moisture, and temperature.
Temperature and Elevation Average Rate of Change 3.5 F per 1000 feet Example: Ashland (~2000 ft) to Mt. Ashland (~7500 ft) 5500 ft x 3.5 F/1000 ft = 19.3 F less (on average)
WEATHER & CLIMATE Controls, continued 6) TOPOGRAPHIC BARRIERS: mountains and islands tend to divert the wind flow vertically causing increased precipitation and/or dryness (windward vs. leeward sides of an island or rain shadows of mountains). Controls moisture and temperature.
Orographic Patterns Figure 8.10
Vertical Zonation - Significant elevational changes in short horizontal distances cause various plant associations to exist in relatively narrow zones on mountain slopes. Elevation changes largely effect how temperature and precipitation vary.
WEATHER & CLIMATE Controls 7) STORMS: create specialized weather circumstances either locally or over large areas.
Macroclimate Mesoclimate Site Environment Slope, Aspect, Sun and Wind Exposure, and Air Drainage Influences Microclimate Canopy and Soil Environment Fruit and Leaf Exposure to Sunlight and Airflow Temperature and Humidity Levels Scales of Climatic Effects Microscale Mesoscale Macroscale
Slope and Aspect Effects on Solar Radiation Receipt Exposure to Sunlight: the direction a given slope faces the sun causes spatial variations in vegetation patterns and growth potential
Sun Path Diagram for 40 N
Relative effects of site aspect (compass direction of slope) or open direction on climate characteristics and crop growth Parameter North North East East South East South South West West North West Initial Growth in Spring Potential for Spring Frost Speed of evaporation in the morning Daily Maximum Canopy Temperatures Radiant heating of crops in summer Retarded Retarded Retarded Advanced Earliest Earliest Advanced Retarded High High Moderate Less Less Less Moderate High Slow Moderate Rapid Moderate Slow Slow Very Slow Slow Minimum Less Less Less Maximum Greater Greater Less Minimum Less Less Less Maximum Greater Greater Moderate Water Needs Low Low Moderate Higher Highest Highest Higher Low Radiant heating of beds in winter Minimum Less Less Moderate Maximum Moderate Less Less
Wind and Air Movement Know the dominant seasonal wind directions and protect from consistently high winds, if necessary. Medford - January Medford - July 38% calm, full range 18% calm, WNW to N
Localized Wind Systems: Small scale winds that have a significant impact on weather & climate, resulting from local pressure gradients. Mountain & Valley Breezes uneven surface heating creates local winds in mountainous regions. Daytime a valley breeze, most evident in the morning to late afternoon hours.
Nighttime a mountain breeze, most evident starting near dusk. Mountain breezes are strongest in winter and are sometimes enhanced by cold air drainage. For any potential gardening plot, the key is provide protection from stronger daytime winds while allowing downslope mountain air to flow past the site.
Cold Air Drainage and Frost Pockets Low-lying areas of a hillside or garden site can be frost pockets in cool to cold climates, especially in spring.
Inversions and Frost Frequency
Inversions and Frost Frequency Important garden site aspects: Thermal zones creates thermal belts ~ 300 feet or more above the valley bottom. Below the mean inversion level, slower start to the growing season and less heat accumulation for ripening.
Measures of Moisture Precipitation: important issues do not follow averages, but seasonality, timing, and frequency.
Measures of Moisture Drought: a temporary dry period. Meteorological drought: related to rainfall amounts Hydrological drought: determined by water levels in reservoirs Agricultural drought: related to the availability of water for crops
Measures of Moisture Relative Humidity: percentage of how close the air is to saturation.
Measures of Moisture Dew Point Temperature: the temperature at which condensation occurs Mean daily average dew point temperature, October
Evapotranspiration (ET): the sum of evaporation and plant transpiration. Measures of Moisture
Climate/Weather Soil Connections Soil Water Balance = Precipitation - Evapotranspiration Which is a function of temperature and humidity. The most important thing to remember is how much water is available to plants. Field Capacity - maximum amount of water the soil can hold before it runs off - occurs during periods of surplus moisture. Wilting Point - the point at which water is mostly unavailable to plants - occurs during deficits. Amount of soil moisture available for plant use is equal to the field capacity minus the wilting point. And describes the concept of a soil-water budget.
Types of Soil Moisture
Soil-Moisture Availability
Soil-Water Budget During periods of deficit you need to know how much water to apply to your garden. Knowing the ET rate tells how much water should be replaced. Should be based on local weather conditions.
Climate Zoning for Plants
Arbor Day Plant Hardiness Zones (USDA, 1990)
Changes in Arbor Day Plant Hardiness Zones (1990 to 2006) For more information go to http://www.arborday.org/media/zones.cfm
http://planthardiness.ars.usda.gov
86 F is the average point at which plants begin suffering physiological damage from heat. The zones range from Zone 1 (less than one heat day) to Zone 12 (more than 210 heat days). Thousands of garden plants have now been coded for heat tolerance. See http://ahs.org/publications/heat_zone_map.htm for more details.
Sunset s climate zones Consider the total climate: length of growing season, timing and amount of rainfall, winter lows, summer highs, humidity.
Zone 7 is found in Northern California and Oregon s Rogue Valley.
Understanding and Realizing Garden Potential Know your regional scale weather and climate controls and understand how they influence your local to site conditions. Maximize garden potential by: Facilitating air flow through and around beds, otherwise cold air will pool and be trapped, putting plants at risk. Know your solar path, removing obstructions if possible. Orient beds and rows to act as solar panels. Know your soil-water budget mostly through site or region evapotranspiration, replenish only what is needed. Use USDA Hardiness Zones to assess winter survival of perennials. Use AHS Plant Heat Zones to assess summer heat stress. Use Sunset Zones to do a holistic climate assessment of individual plant performance and your garden s overall potential. Grow what is suitable but experiment where possible. The only thing about weather and climate that is normal are the statistics!
Available Long-Term Climate Stations in the Rogue Valley Region Station (Elevation) Average July Maximum Temperature (ºF) Average January Minimum Temperature (ºF) Average Mean Growing Season 1 Temperature (ºF) Growing Degree Days (Apr-Oct., 50ºF base) Precipitation (inches) Applegate (1276 ft.) NA 2 NA NA NA 25.2 Ashland (1750 ft.) 86.7 29.1 59.3 2354 19.8 Cave Junction (1280 ft.) 91.9 32.0 62.1 2504 62.6 Grants Pass (960 ft.) 88.8 31.1 60.8 2738 31.0 Medford Airport (1300 ft.) 90.2 30.9 63.1 2910 18.4 Medford Exp.St (1457 ft.) 87.9 30.6 60.6 2436 21.2 Ruch (1549 ft.) 89.6 29.6 61.3 2590 25.8 Williams (1450 ft.) NA 2 NA NA NA 33.6 *All data are from the 1971-2000 climate normals for that station, except for Applegate and Williams which are from monthly climate summaries over for 1979-1998 and 1900-1998, respectively (OCS and WRCC, 1999). 1 April through October 2 NA = data not available.
Median Frost Dates and Frost-Free Period for the Available Long-Term Climate Stations in the Rogue Region Station Median Date of Last Spring Occurrence Median Date of First Fall Occurrence 24ºF 28ºF 32ºF 36ºF 24ºF 28ºF 32ºF 36ºF Applegate (1276 ft.) NA 1 NA NA NA NA NA NA NA NA Frost- Free Period Ashland (1750 ft.) 13-Mar 18-Apr 9-May 29-May 21-Nov 31-Oct 8-Oct 28-Sep 151 Cave Junction (1280 ft.) 24-Feb 13-Apr 8-May 30-May 12-Dec 2-Nov 12-Oct 19-Sep 157 Grants Pass (960 ft.) 22-Feb 2-Apr 30-Apr 20-May 6-Dec 5-Nov 12-Oct 24-Sep 161 Medford Airport (1300 ft.) 26-Feb 29-Mar 28-Apr 18-May 25-Nov 2-Nov 18-Oct 3-Oct 174 Medford Exp.St. (1457 ft.) 7-Mar 1-Apr 14-May 8-Jun 13-Nov 19-Oct 3-Oct 17-Sep 142 Ruch (1549 ft.) 23-Mar 30-Apr 15-May 8-Jun 21-Nov 22-Oct 4-Oct 16-Sep 138 Williams (1450 ft.) NA 1 NA NA NA NA NA NA NA NA Data Source: Oregon Climate Service, 1993 (from 1971-2000 means). 1 NA = data not available.
Weather and Climate Resources Telephone: (541)-779-5990 (NOAA-National Weather Service Forecast Office) Radio: WXL 162.40 mhz (NOAA Weather Radio) Internet: National Weather Service, NOAA, Medford, OR - http://www.wrh.noaa.gov/mfr/ National Weather Service, NOAA, Portland, OR - http://www.wrh.noaa.gov/pqr/ Oregon Climate Service (OCS), Office of the State Climatologist, Oregon State University, Corvallis, OR - http://www.ocs.orst.edu/ Western Regional Climate Center (WRCC), National Oceanic and Atmospheric Administration (NOAA), Reno, NV - http://www.wrcc.dri.edu/ Climate Diagnostics Center (CDC), NOAA-Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, - http://www.cdc.noaa.gov/usclimate/ The Pacific Northwest Cooperative Agricultural Weather Network (AgriMet), U.S. Department of the Interior, Bureau of Reclamation - http://www.usbr.gov/pn/agrimet/ Medford Water Commission Current ET information from the Lawn Watering Infoline, (541) 857-0904. Solar Path Chart University of Oregon s Solar Radiation Monitoring Laboratory (http://solardat.uoregon.edu/sunchartprogram.html) USDA Plant Hardiness Zone Maps - planthardiness.ars.usda.go