The Lower Mississippi River Alluvial Valley (LMRAV) is a key agricultural area within the USA, and although it receives a substantial level of annual rainfall, irrigation remains a requirement to sustain high productivity. Since a large percentage of irrigation comes from limited groundwater sources, predictions of surface and lower atmospheric characteristics associated with convective rainfall processes are critical for planning and managing water resources. While numerical weather models are a key tool in this prediction effort, there is considerable error in the models associated with the correct categorization of regional land use. This is especially true for the LMRAV, where most agricultural land is defined as dry cropland despite the extensive use of irrigation. To improve the accuracy of regional model simulations over the LMRAV, this study investigates the sensitivity of changing the dominate land use category from dry to irrigated cropland within a high-resolution Weather Research and Forecasting (WRF) model simulation. Based on a 5-month simulation (May–Sept. 2016) over the LMRAV, results of the study show that replacing dry cropland with irrigated cropland leads to substantial variations in the low-level thermal and moisture balances. In general, the northern LMRAV was shown to have the greatest increase (decrease) in latent (sensible) heat flux in August and September, with a corresponding increase in 2-m dew point temperature where latent heat flux increased. Additionally, boundary layer heights were shown to decrease over the northern LMRAV over the simulation, likely a result of decreased temperatures resulting from a dampened sensible heat flux.

密西西比河下游冲积河谷（LMRAV）是美国境内的重要农业地区，尽管每年降雨量很高，但灌溉仍是维持高生产力的必要条件。由于大部分灌溉来自有限的地下水源，因此与对流降雨过程相关的地表和较低大气特征的预测对于水资源的规划和管理至关重要。虽然数字天气模型是这项预测工作的关键工具，但与正确的区域土地利用分类相关的模型却存在相当大的误差。对于LMRAV尤其如此，尽管广泛使用灌溉，但大部分农业用地仍被定义为旱地。为了提高LMRAV上区域模型仿真的准确性，这项研究在高分辨率天气研究和预测（WRF）模型模拟​​中研究了将主要土地利用类别从旱地改为灌溉农田的敏感性。基于对LMRAV的5个月模拟（2016年5月至2016年9月），研究结果表明，用灌溉农田替代旱地会导致低水平的热量和水分平衡发生重大变化。通常，在8月和9月，北部LMRAV的潜热通量增加（减少）最大，潜热通量增加的2 m露点温度也相应增加。此外，在整个模拟过程中，边界层的高度在整个北部LMRAV上均降低了，这很可能是由于感热通量受阻导致温度降低的结果。