Science Inventory

Does temperature nudging overwhelm aerosol radiative effects in regional integrated climate models?

Citation:

He, J., T. Glotfelty, K. Yahya, Kiran Alapaty, AND S. Yu. Does temperature nudging overwhelm aerosol radiative effects in regional integrated climate models? ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 154:42-52, (2017). https://doi.org/10.1016/j.atmosenv.2017.01.040

Impact/Purpose:

Highlights • Temperature changes due to nudging are converted to pseudo radiative effects (PRE). • The domain mean PRE is smaller than aerosol effects at surface and in atmosphere. • Nudging could be applied to the integrated models to study ARE at regional scales. • Integrated models with nudging need be treated with caution to study local scale ARE.

Description:

For over two decades, data assimilation (popularly known as nudging) methods have been used for improving regional weather and climate simulations by reducing model biases in meteorological parameters and processes. Similar practice is also popular in many regional integrated meteorology-air quality models that include aerosol direct and indirect effects. However in such multi-modeling systems, temperature changes due to nudging can compete with temperature changes induced by radiatively active & hygroscopic short-lived tracers leading to interesting dilemmas: From weather and climate prediction’s (retrospective or future) point of view when nudging is continuously applied, is there any real added benefit of using such complex and computationally expensive regional integrated modeling systems? What are the relative sizes of these two competing forces? To address these intriguing questions, we convert temperature changes due to nudging into radiative fluxes (referred to as the pseudo radiative forcing, PRF) at the surface and troposphere, and compare the net PRF with the reported aerosol radiative forcing. Results indicate that the PRF at surface dominates PRF at top of the atmosphere (i.e., the net). Also, the net PRF is about 2-4 times larger than estimated aerosol radiative forcing at regional scales while it is significantly larger at local scales. These results also show large surface forcing errors at many polluted urban sites. Thus, operational centers and communities for regional weather and climate predictions may not fully benefit from using computationally expensive integrated models, but there may be added value in using integrated modeling systems at regional/global scales.