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Garden with Insight v1.0 Help: Weather today group


Day length today: The length of the day today in hours. Day length depends on the latitude of the chosen climate station.

Maximum temperature today: The highest temperature today, corresponding to the 'high' on the weather forecast. Hourly temperatures are not simulated, but this would normally probably represent the temperature sometime during the day.

Mean temperature today: The average of the minimum and maximum temperatures today.

Minimum temperature today: The lowest temperature today, corresponding to the 'low' on the weather forecast. Hourly temperatures are not simulated, but this would normally probably represent the temperature sometime during the night.

Radiation today: The amount of solar radiation actually falling on the soil and plants today, after adjustment for cloud cover.

Precipitation (rain or snow) today: The amount of rainfall or snowfall today. Once a day is determined to be a 'wet day' using probabilities, the amount of rain or snow is selected from a skewed normal distribution around the mean daily precipitation for this month.

Relative humidity today: The simulated relative humidity today, which is the ratio of actual vapor pressure to saturated vapor pressure, or how much of the 'room' the air has for water vapor is actually occupied by water vapor. Important in evapotranspiration.

Wind speed today: The average simulated wind speed today. Wind speed is simulated using a modified exponential equation with the long-term monthly average wind speed interpolated (smoothed) for this day of the year and using a parameter to modify the equation.

Wind direction today: The direction of the wind today as measured in degrees from due North. Wind from due South would be at 180 degrees. Affects wind erosion in relation to the orientation of the soil patch's surrounding watershed.

It rained or snowed yesterday: There was some precipitation yesterday. This is used to calculate whether it will rain or snow today, based on the probabilities of precipitation after a 'wet' and 'dry' day.

Latent heat of vaporization today: The amount of heat energy required to evaporate one kilogram of water. Inversely proportional to mean air temperature (the warmer the air, the warmer the water, the easier the evaporation). Used in soil evaporation and plant transpiration.
Vapor pressure deficit today: The saturation vapor pressure (water vapor pressure the air can hold, which depends on mean temperature) minus the actual vapor pressure (which depends on the saturation vapor pressure and the relative humidity). How much more water the air can hold.

Declination angle of the sun today: Today's angle of the sun's rays with respect to the equator. Positive values are north of the equator (March to September) and negative values are south of the equator (September to March). Used in the calculation of day length at a latitude.

Maximum possible radiation (no clouds) today: The greatest amount of solar radiation possible today, considering the latitude of the climate weather station, the changing aspect of the sun with respect to the earth (the declination angle), and the day length. Simulated radiation must always be lower.

Net outgoing radiation if day is clear today: The amount of solar radiation that would reflect back from the earth if there were no clouds today. Increases with high air temperature; decreases with high vapor pressure. Used to calculate net solar radiation for the day.

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Updated: May 4, 1998. Questions/comments on site to webmaster@kurtz-fernhout.com.
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.