Evaluation of Noah-MP Land-Model Uncertainties over Sparsely Vegetated Sites on the Tibet Plateau

Guo Zhang,Fei Chen,Jianduo Li,Yueli Chen,Xindong Peng

doi:10.3390/atmos11050458

Abstract

The water budget and energy exchange over the Tibetan Plateau (TP) region play an important role on the Asian monsoon. However, it is not well presented in the current land surface models (LSMs). In this study, uncertainties in the Noah with multiparameterization (Noah-MP) LSM are assessed through physics ensemble simulations in three sparsely vegetated sites located in the central TP. The impact of soil organic matter on energy flux and water cycles, along with the influence of uncertainties in precipitation are explored using observations at those sites during the third Tibetan Plateau Experiment from 1August2014 to31July2015. The greatest uncertainties are in the subprocesses of the canopy resistance, soil moisture limiting factors for evaporation, runoff (RNF) and ground water, and surface-layer parameterization. These uncertain subprocesses do not change across the different precipitation datasets. More precipitation can increase the annual total net radiation (Rn), latent heat flux (LH) and RNF, but decrease sensible heat flux (SH). Soil organic matter enlarges the annual total LH by ~26% but lessens the annual total Rn, SH, and RNF by ~7%, 7%, and 39%, respectively. Its effect on the LH and RNF at the Nagqu site, which has a sand soil texture type, is greater than that at the other two sites with sandy loam. This study highlights the importance of precipitation uncertainties and the effect of soil organic matter on the Noah-MP land-model simulations. It provides a guidance to improve the Noah-MP LSM further and hence the land-atmosphere interactions simulated by weather and climate models over the TP region.

Highlights

This study is a follow-up on our previous work [1] investigating uncertainties in the Noah with multiparameterization (Noah-MP) land surface model (LSM)simulation for a single cropland site at the southeastern edge of the Tibetan Plateau (TP)
Observations from flux towers at three alpine grassland sites (i.e., Amdo, Nagqu, and Baingoin site) located in central TP from1 August 2014 to 31 July 2015 were used to assess the uncertainties in parameterization scheme combinations of Noah-MP LSM
Based on the identification of subprocesses with great uncertainties and optimal parameterization schemes at these three sites, sensitivity experiments were conducted to explore the impact of soil organic matter on energy flux and water cycles, along with the influence of uncertainties in precipitation

Summary

Introduction

This study is a follow-up on our previous work [1] investigating uncertainties in the Noah with multiparameterization (Noah-MP) land surface model (LSM)simulation for a single cropland site at the southeastern edge of the Tibetan Plateau (TP). We extend the modeling and analytical framework of Zhang et al [1] to three sparsely vegetated sites in the central TP because multiple-site, year-long surface-flux observation data from the third TP experiment that recently became available [2]. These data allow for this type of investigation to be conducted in the data-scarce TP region. The climate regime and land cover types in the southeastern edge of the TP are different from those in the central TP, where alpine grassland is the dominant land cover type

Objectives

Results

Discussion

Conclusion