Collaborative Research: The Great Plains Irrigation Experiment (GRAINEX) for Understanding the Influence of Irrigation on the Planetary Boundary Layer and Weather

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PIs: Rezaul Mahmood, Udaysankar Nair, Eric Rappin, Roger Pielke Sr. and Dallas Staley Scientific Goals: Land use land cover and subsequent changes (LULCC) play an important role in weather and climate systems. Observations and modeling studies suggest that LULCC impacts meso- regional, and potentially global-scale atmospheric circulations, temperature, precipitation, and fluxes.

This research project plans to investigate the impacts of the rapid commencement irrigation and subsequent sustained irrigation on the evolution of planetary boundary layer atmosphere in a region of the Central Great Plains, specifically in Nebraska. We will determine the impacts of the rapid commencement of irrigation in the spring and resultant changes in the land-atmosphere (L-A) coupling at the mesoscale. In addition, this research will investigate the intra-seasonal changes in application in irrigation and their impacts on the boundary layer atmosphere and various processes and mechanisms involved in these changes.

To fulfill the objective of this study the PIs will collect field data in collaboration with the Lower Atmospheric Observation Facilities (LAOF) of the University Consortium for Atmospheric Research (UCAR) and conduct model simulations to further understand the impacts of irrigation on the atmosphere. To further understand land-atmosphere interactions and coupling, this study will use the Weather Research and Forecasting (WRF) model centered on southeastern Nebraska, a region containing strong soil moisture gradients due to widespread application of irrigation in certain areas.

Specifically, we will • Collect observations to quantify changes in land-atmosphere coupling over 100 km x 100

km study area in the Great Plains to temporally rapid and spatially widespread commencement of irrigation. The annual introduction of irrigation is comparable to a binary switch where land surface experiences rapid transformation from water-limited conditions (no irrigation) to high/saturated soil moisture (irrigation).

• Observationally characterize response of boundary layer evolution to changes in land-atmosphere coupling related to irrigation.

• Observe atmospheric circulation features in the study region that are modulated by land-atmosphere coupling.

• Conduct quantitative and modeling analysis to determine the role of irrigation forcing on process pathways that leads to changes in cloud and precipitation formation in the region.

• Develop an observational dataset that allow for the most comprehensive process study of irrigation forcing to date.

Project Location: Nebraska, USA. Start and end dates: One month in 2018 (05/25/18-06/10/18, 7/15/18-07/30/18); and one month in 2019 (05/25/19-06/10/19, 7/15/19-07/30/19).

Facilities to be requested: Simultaneous radiosonde observations, through the deployment of two MISS in York, NE and Lincoln, NE will be requested from LAOF.  These two sites represent irrigated and non-irrigated locations, respectively. 12 EC flux system will also be requested, 6 for irrigated and 6 for non-irrigated areas.

In addition, from CSWR we plan to request three Doppler on Wheels (DOWs), two of which will be sited at the center of an irrigated and non-irrigated domain and one in between but further south compared to the two. Additional radiosonde launches from these two sites will be conducted and launch frequency and timing will replicate launches from York and Lincoln. Two sets of ISS 915 Mhz wind profiler, RASS and laser ceilometer will be requested and operated at these sites.

Number of proposals planned to be submitted to NSF; if planning collaborative proposals, please indicate the number of institutions involved in each: One collaborative proposal, three institutions.

Expected involvement of other funding agencies: None.

Name of the NSF Program Officer: Nick Anderson