scholarly journals Impacts of surface boundary conditions on regional climate model simulations of European climate during the Last Glacial Maximum

2017 ◽  
Vol 44 (10) ◽  
pp. 5086-5095 ◽  
Author(s):  
Patrick Ludwig ◽  
Joaquim G. Pinto ◽  
Christoph C. Raible ◽  
Yaping Shao
Keyword(s):  
Boundary Conditions ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Boundary ◽  
Model Simulations ◽  
European Climate ◽  
Surface Boundary Conditions ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Can Bias Correction of Regional Climate Model Lateral Boundary Conditions Improve Low-Frequency Rainfall Variability?

2017 ◽  
Vol 30 (24) ◽  
pp. 9785-9806 ◽  
Author(s):  
Eytan Rocheta ◽  
Jason P. Evans ◽  
Ashish Sharma
Keyword(s):  
Boundary Conditions ◽  
Regional Climate Model ◽  
Bias Correction ◽  
Climate Model ◽  
Regional Climate ◽  
Low Frequency ◽  
Lateral Boundary ◽  
Model Simulations ◽  
Low Frequency Variability ◽  
Climate Model Simulations

Global climate model simulations inherently contain multiple biases that, when used as boundary conditions for regional climate models, have the potential to produce poor downscaled simulations. Removing these biases before downscaling can potentially improve regional climate change impact assessment. In particular, reducing the low-frequency variability biases in atmospheric variables as well as modeled rainfall is important for hydrological impact assessment, predominantly for the improved simulation of floods and droughts. The impact of this bias in the lateral boundary conditions driving the dynamical downscaling has not been explored before. Here the use of three approaches for correcting the lateral boundary biases including mean, variance, and modification of sample moments through the use of a nested bias correction (NBC) method that corrects for low-frequency variability bias is investigated. These corrections are implemented at the 6-hourly time scale on the global climate model simulations to drive a regional climate model over the Australian Coordinated Regional Climate Downscaling Experiment (CORDEX) domain. The results show that the most substantial improvement in low-frequency variability after bias correction is obtained from modifying the mean field, with smaller changes attributed to the variance. Explicitly modifying monthly and annual lag-1 autocorrelations through NBC does not substantially improve low-frequency variability attributes of simulated precipitation in the regional model over a simpler mean bias correction. These results raise questions about the nature of bias correction techniques that are required to successfully gain improvement in regional climate model simulations and show that more complicated techniques do not necessarily lead to more skillful simulation.

scholarly journals Climate simulations and pollen data reveal the distribution and connectivity of temperate tree populations in eastern Asia during the Last Glacial Maximum

2020 ◽  
Vol 16 (6) ◽  
pp. 2039-2054
Author(s):  
Suzanne Alice Ghislaine Leroy ◽  
Klaus Arpe ◽  
Uwe Mikolajewicz ◽  
Jing Wu
Keyword(s):  
Climate Model ◽  
Deciduous Tree ◽  
Eastern Asia ◽  
Pollen Data ◽  
Model Simulations ◽  
Climate Simulations ◽  
Temperate Deciduous ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Publications on temperate deciduous tree refugia in Europe are abundant, but little is known about the patterns of temperate tree refugia in eastern Asia, an area where biodiversity survived Quaternary glaciations and which has the world's most diverse temperate flora. Our goal is to compare climate model simulations with pollen data in order to establish the location of glacial refugia during the Last Glacial Maximum (LGM). Limits in which temperate deciduous trees can survive are taken from the literature. The model outputs are first tested for the present by comparing climate models with published modern pollen data. As this method turned out to be satisfactory for the present, the same approach was used for the LGM. Climate model simulations (ECHAM5 T106), statistically further downscaled, are used to infer the temperate deciduous tree distribution during the LGM. These were compared with available fossil temperate tree pollen occurrences. The impact of the LGM on the eastern Asian climate was much weaker than on the European climate. The area of possible tree growth shifts only by about 2∘ to the south between the present and the LGM. This contributes to explaining the greater biodiversity of forests in eastern Asia compared to Europe. Climate simulations and the available, although fractional, fossil pollen data agree. Therefore, climate estimations can safely be used to fill areas without pollen data by mapping potential refugia distributions. The results show two important areas with population connectivity: the Yellow Sea emerged shelf and the southern Himalayas. These two areas were suitable for temperate deciduous tree growth, providing corridors for population migration and connectivity (i.e. less population fragmentation) in glacial periods. Many tree populations live in interglacial refugia, not glacial ones. The fact that the model simulation for the LGM fits so well with observed pollen distribution is another indication that the model used is good enough to also simulate the LGM period.

Surface Boundary Conditions for Mesoscale Regional Climate Models

2005 ◽  
Vol 9 (18) ◽  
pp. 1-28 ◽  
Author(s):  
Xin-Zhong Liang ◽  
Hyun I. Choi ◽  
Kenneth E. Kunkel ◽  
Yongjiu Dai ◽  
Everette Joseph ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Clay Fraction ◽  
Value Added ◽  
Quality Data ◽  
Surface Boundary ◽  
Surface Boundary Conditions ◽  
Vegetation Characteristic

Abstract This paper utilizes the best available quality data from multiple sources to develop consistent surface boundary conditions (SBCs) for mesoscale regional climate model (RCM) applications. The primary SBCs include 1) fields of soil characteristic (bedrock depth, and sand and clay fraction profiles), which for the first time have been consistently introduced to define 3D soil properties; 2) fields of vegetation characteristic fields (land-cover category, and static fractional vegetation cover and varying leaf-plus-stem-area indices) to represent spatial and temporal variations of vegetation with improved data coherence and physical realism; and 3) daily sea surface temperature variations based on the most appropriate data currently available or other value-added alternatives. For each field, multiple data sources are compared to quantify uncertainties for selecting the best one or merged to create a consistent and complete spatial and temporal coverage. The SBCs so developed can be readily incorporated into any RCM suitable for U.S. climate and hydrology modeling studies, while the data processing and validation procedures can be more generally applied to construct SBCs for any specific domain over the globe.

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