Contrasting Responses of Local Climate to the Perturbation of Atmospheric Boundary Layer Winds Linked to Land-Atmosphere Interactions

The atmospheric boundary layer (ABL) is an interface through which the land surface influences the atmosphere and is crucial to land-atmosphere (L-A) interactions. Winds are an important element of the ABL, but their role in L-A interactions is still partly unclear. Here, we use regional climate model experiments to investigate the impact of ABL winds on intraseasonal climate variabilities in East Asia. Two ensemble experiments were performed: one is a control ensemble, and the other is a perturbed ensemble, in which the ABL winds are shuffled from corresponding ensemble members of the control ensemble to produce a random perturbation of ABL winds. We found that the climates of the ensemble members become less similar in humid southern China, but generally more similar in semiarid northern China/Mongolia (NCM), especially for the mean values of several variables. The weather in southern China strongly responds to ABL winds and becomes less similar after perturbation. In NCM, however, the strong L-A positive feedbacks, which involve wind field change in response to land surface changes and tend to cause large weather and climate anomalies, are weakened by the ABL wind perturbations. Thus, the inter-member divergences of related variables, including surface temperature, sensible heat flux, soil moisture, and to some extent precipitation, are smaller and their time series are more similar. Clearly, the different L-A interactions in these two regions are the main reason for the contrasting responses of local climate to the ABL wind perturbations.

Automated summary

By conducting regional climate model experiments, it was found that atmospheric boundary layer (ABL) winds have an impact on intraseasonal climate variabilities in East Asia. The research revealed that climates became less similar in humid southern China but more similar in semiarid northern China/Mongolia (NCM) after ABL wind perturbations. The contrasting responses of local climate to ABL wind perturbations were mainly due to different land-atmosphere interactions in these two regions.