This is a partial summary / review of both the seminar talk given here by J. Adegoke and his recent paper on the same topic - coauthored by R. Pielke and A. Carleton.

This talk was about the role of areas of contrasting forest and agricultureal land in the formation of convective clouds in the Midwest U.S., and simulations of the impact of U.S. Plains agriculture on planetary boundary layer processes such as surface energy partitioning and near-ground temperature.

There have been many observational studies of convective clouds and their relationship to contrasting forested and agricultureal land cover. For instance Carleton et. al. (1994), Rabin and Martin (1996) and O’Neal (1996). Previous studies of this sort were short-term case studies, and did not study these effects over multiple years. This talk focused on two main questions. What associations exist between land cover and convective clouds under weak, moderate, and strong synoptic flow? How do the boundaries between farmland and forests affect the convective could formation?

His observational study used long-term satellite data of both visible and infrared varieties to judge several parameters of the cloud. He focused mostly on the weakest synopic flow regime. During the times of weak synoptic flow, cloud development peaked earlier, and persisted longer, over the cropland than forested or the boundary areas. The clouds were taller (cloud top temperature was lower) over the cropland. And the mid-afternoon albedo was 20% greater over the cropland. At least in Michigan. This is quite different that what seen over Missouri. He postulated that the time difference was due to the differences in the planetary boundary layer moisture and temperature characteristics. The lower atmosphere was found to be drier in Michigan by radiosonde measurements, where the cloud growth is more vigorous over the forests.

He then talked about his modelling study where he investigated the affects of irrigation on regional climate. He found that irrigated farmland cooled the ground temperatures and there was an increase in water vapor and latent heat flux. The latent heat by itself would warm the lower atmosphere and ground. The missing piece is the sensible heat flux which cools the ground. In this case, it appears the sensible heat flux is more important than the sensible heat flux.

In all it was a good talk, though I do have some questions - some of which were asked at the seminar.

• • How does this regional cooling affect areas outside of the irrigated areas? Are they warmed by the flux of energy out of the irrigated areas?
• • How does this regional climate change affect global climate change? Is it included in the current global climate models? If not, can it be?
• • Is this same effect likely to be seen at other areas around the U.S.? the World?
• • Can this research be used to more accurately predict convective systems in the Midwest? the rest of the World?

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