HR: 14:25h
AN: H43I-03    [Abstracts]
TI: Investigation of the Land Use Changes in California using MM5-CLM3
AU: * JIn, J
EM: jimingjin@lbl.gov
AF: UC-Berkeley Natinal Lab, 90-1116 One Cyclotron Road, Berkeley, CA 94720 United States
AU: Miller, N L
EM: nlmiller@lbl.gov
AF: UC-Berkeley Natinal Lab, 90-1116 One Cyclotron Road, Berkeley, CA 94720 United States
AB: As part of an investigation of the impacts of land use change on California's hydroclimate, we have coupled and applied the National Center for Atmospheric Research (NCAR) Community Land Model version 3 (CLM3) with the Penn State-NCAR fifth generation Mesoscale Model version 3 (MM5). CLM3 physically describes the mass and heat transfer with well developed lateral hydrology, crop, and snow schemes, where interactions among the vegetation, soil, and snow are functions of the CLM3 mass and energy equations. Additionally, a sophisticated surface albedo scheme was adopted here to improve the surface energy balance simulations, and to further understand sensitivities associated with land use change. The introduction of a maximum of 8 sub-cells within each CLM3 cell has shown a significant improvement in the accuracy of land surface heterogeneous characterizations and the land surface-atmosphere water and energy flux exchanges. The coupled MM5-CLM3 atmosphere-land model used here has demonstrated significant improvements in our regional climate simulations, when compared to the original MM5. To better understand how California land use changes affect local hydroclimate processes, a 30-km resolution version of MM5-CLM3 was used to perform a set of one-year sensitivity simulations, control and change, for the period 1 October 1995 to 30 September 1996. The control simulation is forced with modern land use descriptions with a large percentage of California's low lying regions represented as croplands, and the change is represented by grasslands that were present in these same regions prior to the 1950s. Initial results show that the control simulations (croplands) indicate that temperature, precipitation, and snow agree well with observations. The major differences between the control and change simulations were found to occur during the summer season. The control simulation, where the pre-1950s grasslands were replaced with croplands, indicated an increase in the surface albedo due to the large difference between the vegetation types. Additionally, the increase in surface albedo in the control simulation had a reduction in the surface solar radiation absorption, but the lowered surface evaporation due to the harvesting of the crops, leaving bare soil resulted in more energy on the surface. Hence, the net effects of land use changes result in an increase in the surface temperature. The impact of the land use changes during the irrigation-growing season is still under investigation.
UR: http://esd.lbl.gov/RCC
DE: 1807 Climate impacts
DE: 1814 Energy budgets
DE: 1818 Evapotranspiration
DE: 1833 Hydroclimatology
DE: 1840 Hydrometeorology
SC: Hydrology [H]
MN: Fall Meeting 2005