Neural Network–Based Sensitivity Analysis of Summertime Convection over the Continental United States

Abstract

Although land-atmosphere coupling is thought to play a role in shaping the mean climate and its variability, it remains difficult to quantify precisely. The present study aims to isolate relationships between early morning surface turbulent fluxes partitioning [i.e., evaporative fraction (EF)] and subsequent afternoon convective precipitation frequency and intensity. A general approach involving statistical relationships among input and output variables, known as sensitivity analysis (SA), is used to develop a reduced complexity metamodel of the linkage between EF and convective precipitation. Two additional quantities characterizing the early morning convective environment, convective triggering potential (CTP) and low-level humidity (HIlow) deficit, are included. The SA approach is applied to the North American Regional Reanalysis (NARR) for June-August (JJA) conditions over the entire continental United States, Mexico, and Central America domain. Five land-atmosphere coupling regimes are objectively characterized based on CTP, HIlow, and EF. Two western regimes are largely atmospherically controlled, with a positive link to CTP and a negative link to HIlow. The other three regimes occupy Mexico and the eastern half of the domain and show positive links to EF and negative links to HIlow, suggesting that both surface fluxes and atmospheric humidity play a role in the triggering of rainfall in these regions. The regimes associated with high mean EF also tend to have high sensitivity of rainfall frequency to variations in EF. While these results may be sensitive to the choice of dataset, the approach can be applied across observational, reanalysis, and model datasets and thus represents a potentially powerful tool for intercomparison and validation as well as for characterizing land-atmosphere interaction regimes.

Confounding factors in determining causal soil moisture‐precipitation feedback

“…More recently, Aires et al . [] performed a sensitivity analysis using reanalysis data and a neural network to identify the links between morning surface and atmospheric properties and afternoon precipitation. However, while suggestive, these correlations and metrics fall short of proving causation.…”

Relation between Convective Rainfall Properties and Antecedent Soil Moisture Heterogeneity Conditions in North Africa

“…In addition, as was already mentioned earlier, soil moisture heterogeneity impact on AR amount and possibly AR size will rather occur via the contribution of added moisture due to convergence to the total moisture amount rather than via increased strength of updrafts [46]. Given this complexity of factors and non-linear relationships involved in the rainfall evolution, quantification of soil moisture impact on rainfall amount has proven to be notoriously difficult in the past [81][82][83][84] and will likely remain so.…”

Land–Atmosphere Coupling at the Southern Great Plains Atmospheric Radiation Measurement (ARM) Field Site and Its Role in Anomalous Afternoon Peak Precipitation

“…2f), which can act to support precipitation and, in turn, soil moistening (Figs. 2c; Aires et al 2014).…”

“…If the LFC and lifting condensation level (LCL) are lowered far enough, then they will meet the PBL top and trigger convection (Aires et al 2014;Findell and Eltahir 2003). Findell et al (2011) showed that high evaporation rates in moisturerich areas east of the Mississippi River and in Mexico increased the probability of afternoon rainfall.…”