Spatial Precipitation Patterns: Where does it rain in Idaho and Why?
Understanding the basic processes and conditions that produce precipitation in not quite enough to be able to predict where, when, and how much it is going to rain. We need one more piece of the puzzle.
Recall that rain can't happen unless condensation occurs and there is atmospheric instability. These two conditions are the product of atmospheric lifting: when air masses are forced upward to higher altitudes and expand and cool as a result of being forced up in altitude. The four types of lifting (frontal, convective, orographic, and convergent) are all present in Idaho and the Pacific Northwest, but produce very different weather patterns and types of precipitation. Let's look at how these different lifting processes work to produce the precipitation climatology shown on the map and climographs below.
The amount of total annual precipitation that falls across Idaho is spatially quite variable, with the driest parts of the state in Snake River Plain receiving less than 10 inches of precipitation in an average year, while mountains in the Bitterroot and northern Idaho panhandle can receive more than 100 inches in an average year.
Recall that rain can't happen unless condensation occurs and there is atmospheric instability. These two conditions are the product of atmospheric lifting: when air masses are forced upward to higher altitudes and expand and cool as a result of being forced up in altitude. The four types of lifting (frontal, convective, orographic, and convergent) are all present in Idaho and the Pacific Northwest, but produce very different weather patterns and types of precipitation. Let's look at how these different lifting processes work to produce the precipitation climatology shown on the map and climographs below.
The amount of total annual precipitation that falls across Idaho is spatially quite variable, with the driest parts of the state in Snake River Plain receiving less than 10 inches of precipitation in an average year, while mountains in the Bitterroot and northern Idaho panhandle can receive more than 100 inches in an average year.
Note the differences in magnitude of precipitation observed at these four sites as well as the different times of the year the precipitation falls. Most of the western half of Idaho including all of the panhandle receive the most precipitation during the winter months associated with west-to-east moving weather systems. Very evident in the precipitation map is the overall increase in precipitation in the Idaho panhandle as one moves further east. What process is responsible for this increase?
Boise and Pocatello receive the least precipitation. Consider at least two reasons behind this. Note that Boise is around the same elevation as Wallace, Idaho and slightly higher in elevation than Moscow, yet receives less than half of the total annual precipitation of Wallace or Moscow.
The eastern two most locations have their wettest months in late spring. During the spring, the land surface begins to heat up and when combined with enough moisture results in what sort of precipitation process?
Finally, review all four climographs and simultaneously monthly temperature and precipitation. Which location do you think receives the most average total snowfall per year? How about the least?
The diversity of spatial precipitation patterns observed in Idaho associated with different lifting mechanisms is consistent with the diversity of precipitation patterns across the Earth globally. Log in to BBLearn and under Module 4, complete "Assignment 4.6: Spatial Patterns of Precipitation."
Boise and Pocatello receive the least precipitation. Consider at least two reasons behind this. Note that Boise is around the same elevation as Wallace, Idaho and slightly higher in elevation than Moscow, yet receives less than half of the total annual precipitation of Wallace or Moscow.
The eastern two most locations have their wettest months in late spring. During the spring, the land surface begins to heat up and when combined with enough moisture results in what sort of precipitation process?
Finally, review all four climographs and simultaneously monthly temperature and precipitation. Which location do you think receives the most average total snowfall per year? How about the least?
The diversity of spatial precipitation patterns observed in Idaho associated with different lifting mechanisms is consistent with the diversity of precipitation patterns across the Earth globally. Log in to BBLearn and under Module 4, complete "Assignment 4.6: Spatial Patterns of Precipitation."