Impact of agricultural practice on regional climate in a coupled land surface mesoscale model

Abstract

[1] The land surface has been shown to form strong feedbacks with climate due to linkages between atmospheric conditions and terrestrial ecosystem exchanges of energy, momentum, water, and trace gases. Although often ignored in modeling studies, land management itself may form significant feedbacks. Because crops are harvested earlier under drier conditions, regional air temperature, precipitation, and soil moisture, for example, affect harvest timing, particularly of rain-fed crops. This removal of vegetation alters the land surface characteristics and may, in turn, affect regional climate. We applied a coupled climate model (MM5) and land surface model (LSM1) to examine the effects of early and late winter wheat harvest on regional climate in the Department of Energy Atmospheric Radiation Measurement (ARM) Climate Research Facility in the Southern Great Plains, where winter wheat accounts for 20% of the land area. Within the harvested, winter wheat region, simulated 2 m air temperature was 1.3°C warmer in the early harvest scenario at midday averaged over the 2 weeks following harvest. Soils in the harvested area were drier and warmer in the top 10 cm and wetter in the 10-20 cm layer compared to those in the late harvest. Midday soils were 2.5°C warmer in the harvested area at midday averaged over the 2 weeks following harvest. Harvest also dramatically altered latent and sensible heat fluxes. Although differences between scenarios diminished once both scenarios were harvested, the short-term impacts of land management on climate were comparable to those from land cover change demonstrated in other studies.

Spatiotemporal Variations in Growing Season Exchanges of CO2, H2O, and Sensible Heat in Agricultural Fields of the Southern Great Plains

“…13 14 Latent heat (like NEE) also exhibited the seasonality of the different crops, with the exception 15 that soil moisture evaporation continued into the summer after plant crops were harvested and 16 photosynthesis had stopped (Figures 4a and 4b). For example, LE increased briefly in the winter-17 wheat fields near day 210 after a rain event (Figure 4b).…”

Development of an Implementation Plan for Atmospheric Carbon Monitoring in California

“…The integration of LSM1 with MM5 was accomplished via the established interface for the OSULSM, with changes in the interface to account for partitioning shortwave radiation between diffuse and direct components (Chen et al 2001). Previous work has shown that the coupled model's predictions of energy fluxes, near-surface air temperatures, and soil moisture and temperature compared favorably to data collected during a previous field campaign (Betts et al 1998;Cooley et al 2004). …”

SGP Cloud and Land Surface Interaction Campaign (CLASIC): Science and Implementation Plan

“…In the SGP region, winter wheat accounts for about 20% of the land area (Cooley et al 2005). The winter wheat harvest during mid-to-late June contributes to the most dynamic period of the year, when atmospheric and land surface conditions undergo rapid changes.…”