The Great Plains Irrigation Experiment (GRAINEX) Rappin, Eric; Mahmood, Rezaul; Nair, Udaysankar ...
Bulletin of the American Meteorological Society,
09/2021, Letnik:
102, Številka:
9
Journal Article
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Extensive expansion in irrigated agriculture has taken place over the last half century. Due to increased irrigation and resultant land-use–land-cover change, the central United States has seen a ...decrease in temperature and changes in precipitation during the second half of the twentieth century. To investigate the impacts of widespread commencement of irrigation at the beginning of the growing season and continued irrigation throughout the summer on local and regional weather, the Great Plains Irrigation Experiment (GRAINEX) was conducted in the spring and summer of 2018 in southeastern Nebraska. GRAINEX consisted of two 15-day intensive observation periods. Observational platforms from multiple agencies and universities were deployed to investigate the role of irrigation in surface moisture content, heat fluxes, diurnal boundary layer evolution, and local precipitation. This article provides an overview of the data collected and an analysis of the role of irrigation in land–atmosphere interactions on time scales from the seasonal to the diurnal. The analysis shows that a clear irrigation signal was apparent during the peak growing season in mid-July. This paper shows the strong impact of irrigation on surface fluxes, near-surface temperature and humidity, and boundary layer growth and decay.
The convective planetary boundary layer (PBL) integrates land-atmosphere interactions over regional spatial scales and diurnal temporal scales. Previous attempts to infer surface energy and water ...budgets from observations of the PBL have been constrained by difficulties in monitoring and estimating the processes that control PBL evolution. This research presents an empirical and modeling investigation of land-atmosphere interactions focusing on the utility of remote sensing of the PBL. An energy conservation approach applied to 132 sets of daily PBL and land surface observations from the Atmospheric Radiation Measurement Cloud and Radiation Test Bed in the Southern Great Plains (ARM-SGP) reveals limitations to using energy budget methods to estimate surface fluxes on diurnal time scales. At the same time, statistical analyses demonstrate that observable properties of the PBL are directly related to land surface conditions and a methodology is established to estimate surface fluxes and moisture conditions that does not require detailed land surface models or parameterizations. These relationships vary as a function of surface properties and atmospheric conditions and are examined in detail using a coupled PBL/land-surface model in association with observational data. More importantly, the results from these analyses identify feedbacks in the land-atmosphere system that are not included in current models of the PBL. The feedbacks and relationships also provide insight regarding the link between surface fluxes and PBL structure, and can be used to estimate surface conditions from routine observations of the PBL. Vertical temperature profiles retrieved from radiances measured by MODIS and AIRS provide information related to PBL structure. However, a comparison of retrieved profiles with radiosonde measurements shows that MODIS does not have sufficient spectral resolution to accurately discern information on temperatures in the PBL. Similarly, AIRS profiles are limited by biases introduced by retrieval algorithms. Despite these limitations, information on PBL structure can be extracted from AIRS retrievals using empirical relationships. The results also demonstrate that surface conditions are strongly correlated with AIRS radiances and that measurements in as few as five bands are able to explain greater than 80 percent of the variance in observed near-surface soil moisture and sensible heat flux.
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