Jan Polcher

Jan Polcher
French National Centre for Scientific Research | CNRS · Laboratoire de Météorologie Dynamique (LMD)

About

240
Publications
50,340
Reads
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13,612
Citations
Introduction
Career Goal : To enhance our understanding of the global environment and to predict its evolution and impacts on human activities using modeling tools.
Additional affiliations
January 2019 - December 2021
WCRP
Position
  • Chair
Description
  • https://www.gewex.org/
January 2005 - January 2010
French National Centre for Scientific Research
Position
  • Coordination of the AMMA FP6 Project
Description
  • www.amma-eu.org
January 1999 - January 2003
WCRP
Position
  • Global Land-Atmosphere System Study (GLASS)
Description
  • http://www.gewex.org/glass.html

Publications

Publications (240)
Article
Droughts can have strong environmental and socioeconomic impacts in the Mediterranean region, in particular for countries relying on rain-fed agricultural production, but also in areas in which irrigation plays an important role and in which natural vegetation has been modified or is subject to water stress. The purpose of this review is to provide...
Article
Full-text available
Tropical floodplains have a significant impact on the regional water cycle and on land-atmosphere interaction but are not always considered in Land Surface Models (LSMs) or in Earth system models. This study evaluates the importance of representing tropical floodplains in an LSM to provide realistic river discharges, evapotranspiration fluxes and o...
Article
Full-text available
Abstract This study presents the global climate model IPSL‐CM6A‐LR developed at Institut Pierre‐Simon Laplace (IPSL) to study natural climate variability and climate response to natural and anthropogenic forcings as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). This article describes the different model components, t...
Article
Full-text available
Ensemble estimates based on multiple datasets are frequently applied once many datasets are available for the same climatic variable. An uncertainty estimate based on the difference between the ensemble datasets is always provided along with the ensemble mean estimate to show to what extent the ensemble members are consistent with each other. Howev...
Preprint
Full-text available
Abstract. The streamflow of the Yellow River is strongly affected by human activities of irrigation and dam regulation. Many attribution studies focused on the long-term trend of discharge, yet the contributions of these anthropogenic factors to streamflow fluctuations have not been well quantified. This study aims to quantify the roles of irrigati...
Article
Increased human water use combined with climate change have aggravated water scarcity from the regional to global scales. However, the lack of spatially detailed datasets limits our understanding of the historical water use trend and its key drivers. Here, we present a survey-based reconstruction of China’s sectoral water use in 341 prefectures dur...
Article
Full-text available
The study of the spatio-temporal dynamics of surface soil moisture (SSM) drydowns integrates the soil response to climatic conditions, drainage and land cover and is key to advances in our knowledge of the soil–atmosphere water exchange. SSM drydowns have also been employed to compare soil moisture spatio-temporal behaviour between different data s...
Article
Full-text available
In China, irrigation is widespread in 40.7% cropland to sustain crop yields. By its action on water cycle, irrigation affects water resources and local climate. In this study, a new irrigation module, including flood and paddy irrigation technologies, was developed in the ORCHIDEE-CROP land surface model which describes crop phenology and growth in...
Article
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Abstract This study estimated the sensitivity of rainfall characteristics (rainfall amount, rainfall frequency, rainfall intensity, and rainfall extremes based on 30-min intervals) to land-surface conditions over Southeast Asia, which has a wet land surface during the rainy season. To obtain the regional difference in sensitivity and simulate basic...
Article
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The WMO convened the “Science Summit on Seamless Research for Weather, Climate, Water, and Environment” to guide the Commission for Atmospheric Sciences (CAS-17) on future scientific research needs and requirements. Whether on an urban or planetary scale, covering timescales of a few minutes or a few decades, the societal need for more accurate wea...
Article
Full-text available
Precipitation minus evaporation over continents is the freshwater flux which can be sustainably exploited by mankind. Over a catchment and longer time periods, this flux is also the amount of water which flows into the ocean. An essential question for semi-arid areas of the world is how well this freshwater flux can be estimated and predicted to ev...
Article
Full-text available
This study focuses on the Iberian Peninsula and investigates the propagation of precipitation uncertainty, and its interaction with hydrologic modeling, in global water resource reanalysis. Analysis is based on ensemble hydrologic simulations for a period spanning 11 years (2000-2010). To simulate the hydrological variables of surface runoff, sub-s...
Poster
Full-text available
A key challenge in the projection of climate change (CC) impacts on hydrological hazards is the uncertainty, mainly from climate projections and hydrological modeling. Therefore, it is the state of the art to use the multi-model ensemble (MME) based information for quantifying potential CC impacts. A considerable amount of studies have been done ba...
Article
Full-text available
The Coordinated Regional Climate Downscaling Experiment (CORDEX) is a scientific effort of the World Climate Research Program (WRCP) for the coordination of regional climate initiatives. In order to accept an experiment, CORDEX provides experiment guidelines, specifications of regional domains, and data access and archiving. CORDEX experiments are...
Article
Full-text available
The uncertainty among climatological datasets can be characterized as the variance in space and time between various estimates of the same quantity. However, some of the current uncertainty estimates only evaluate variations in one single dimension (time or space) due to the limitation of estimation methodology as averaging variation is necessary f...
Article
Full-text available
The Mediterranean region is one of the climate hotspots where the climate change impacts are both pronounced and documented. The HyMeX (Hydrometeorological Mediterranean eXperiment) aims to improve our understanding of the water cycle from the meteorological to climate scales. However, monitoring the water cycle with Earth observations (EO) is stil...
Article
Full-text available
The river routing scheme (RRS) in the Organising Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) land surface model is a valuable tool for closing the water cycle in a coupled environment and for validating the model performance. This study presents a revision of the RRS of the ORCHIDEE model that aims to benefit from the high-resolution topo...
Article
Full-text available
The bias in atmospheric variables and that in model computation are two major causes of failures in discharge estimation. Attributing the bias in discharge estimation becomes difficult if the forcing bias cannot be evaluated and excluded in advance in places lacking qualified meteorological observations, especially in cold and mountainous areas (e....
Article
Full-text available
As an essential source of freshwater river flow comprises ~80% of the water consumed in China. Per capita water resources in China are only a quarter of the global average, and its economy is demanding in water resources; this creates an urgent need to quantify the factors that contribute to changes in river flow. Here, we used an offline process-b...
Article
Full-text available
Soil moisture plays a key role in water, carbon and energy exchanges between the land surface and the atmosphere. Therefore, a better representation of this variable in the Land-Surface Models (LSMs) used in climate modelling could significantly reduce the uncertainties associated with future climate predictions. In this study, the ESA-CCI soil moi...
Article
Full-text available
The Coordinated Regional Climate Downscaling Experiment (CORDEX) is a scientific effort of the World Climate Research Program (WRCP) for the coordination of regional climate initiatives. In order to accept an experiment, CORDEX provides experiment guidelines, specifications of regional domains and data access/archiving. CORDEX experiments are impor...
Article
Full-text available
Soil moisture is a key variable of land surface hydrology, and its correct representation in land surface models is crucial for local to global climate predictions. The errors may come from the model itself (structure and parameterization) but also from the meteorological forcing used. In order to separate the two source of errors, four atmospheric...
Article
Full-text available
This study focuses on the Iberian Peninsula and investigates the propagation of precipitation uncertainty, and its interaction with hydrologic modelling, in global water resources reanalysis. Analysis is based on ensemble hydrologic simulations for a period spanning 11 years (2000–2010). To simulate the hydrological variables of surface runoff, sub...
Article
Full-text available
River discharge plays an important role in earth's water cycle, but it is difficult to estimate due to un-gauged rivers, human activities and measurement errors. One approach is based on the observed flux and a simple annual water balance model (ignoring human processes) for un-gauged rivers, but it only provides annual mean values which is insuffi...
Article
Full-text available
Integration techniques are used to combine Earth Observation (EO) datasets to study the Water Cycle (WC). By merging several datasets, they reduce uncertainty and introduce coherency among them. Several EO integration methods are presented and compared: The Optimal Selection (OS) simply choses the best individual datasets. Simple Weighting (SW) is...
Article
Full-text available
This study presents a revised river routing scheme (RRS) for the Organising Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) land surface model. The revision is carried out to benefit from the high resolution topography provided the Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales (HydroSHEDS), processed to...
Article
Full-text available
Physically consistent descriptions of land surface hydrology are crucial for planning human activities that involve freshwater resources, especially in light of the expected climate change scenarios. We assess how atmospheric forcing data uncertainties affect land surface model (LSM) simulations by means of an extensive evaluation exercise using a...
Article
Full-text available
The bias in atmospheric variables as well as that in model computation are two major causes of failures in discharge estimation. Attributing the bias in discharge estimation becomes difficult if there is a lack of qualified meteorological observations. The problem is more complicated over the mountainous area where strong orographic effects exist a...
Article
Full-text available
The river discharge plays an important role in earth’s water cycles, but it is difficult to estimate due to un-gauged rivers, human activities, and measurement errors. One approach is based on the observed flux and a simple annual water balance model (ignoring human processes) for ungauged rivers, but it only provides annual mean values which is in...
Article
Full-text available
Four atmospheric forcing datasets: GSWP3 (Global Soil Wetness Project Phase 3), PGF (Princeton Global meteorological Forcing), CRU-NCEP (Climatic Research Unit-National Center for Environmental Prediction) and WFDEI (WATCH Forcing Data methodology applied to ERA-Interim reanalysis data), are used to drive simulations in China by the land surface mo...
Article
Full-text available
Lateral transfer of carbon (C) from terrestrial ecosystems into the inland water network is an important component of the global C cycle, which sustains a large aquatic CO2 evasion flux fuelled by the decomposition of allochthonous C inputs. Globally, estimates of the total C exports through the terrestrial–aquatic interface range from 1.5 to 2.7 P...
Article
Full-text available
The dataset presented here consists of an ensemble of 10 global hydrological and land surface models for the period 1979–2012 using a reanalysis-based meteorological forcing dataset (0.5° resolution). The current dataset serves as a state of the art in current global hydrological modelling and as a benchmark for further improvements in the coming y...
Article
This paper presents a review of the state-of-the-art in understanding and quantification of the Mediterranean heat and mass (i.e. salt and water) budgets. The budgets are decomposed into a basin averaged surface component, lateral boundary components (through the Gibraltar and the Dardanelles Straits), a river input component and a content change c...
Technical Report
Full-text available
This report describes the tier-2 water resources reanalysis (WRR2) development, implementation and data structure and storage. The Earth2Observe WRR1 dataset consisted of an ensemble of ten global hydrological and land surface models for the 1979-2012 period using a meteorological forcing dataset based on reanalysis. The WRR1 dataset was develope...
Article
Full-text available
Lateral transfer of carbon (C) from terrestrial ecosystems into the inland water network is an important component of the global C cycle, which sustains a large aquatic CO2 evasion flux fueled by the decomposition of allochthonous C inputs. Globally, estimates of the total C exports through the terrestrial-aquatic interface range from 1.5 to 2.7 Pg...
Article
Full-text available
Comparing streamflow simulations against observations has become a straightforward way to evaluate a land surface model’s (LSM) ability in simulating water budget within a catchment. Using a meso-scale river routing scheme (RRS), this study evaluates simulated water budgets over the upper Ouémé River basin derived from 14 LSMs within the framework...
Article
Full-text available
L-band radiometry is considered to be one of the most suitable techniques to estimate surface soil moisture (SSM) by means of remote sensing. Brightness temperatures are key in this process, as they are the main input in the retrieval algorithm which yields SSM estimates. The work exposed compares brightness temperatures measured by the SMOS missio...
Article
Full-text available
The dataset presented here consists of an ensemble of ten global hydrological and land surface models for the period 1979–2012 using a reanalysis-based meteorological forcing dataset (0.5° resolution). The current dataset serves as a state-of-the-art in current global hydrological modelling and as a benchmark for further improvements in the coming...
Article
Full-text available
Canopy structure is one of the most important vegetation characteristics for land–atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the ORCHIDEE-CAN v1.0 land surface model (Organi...
Presentation
Full-text available
Global-scale evaluation of the hydrology simulated by ORCHIDEE and sensitivity to the atmospheric forcing
Poster
Full-text available
Precipitation is arguably one of the most important forcing variables that drive terrestrial water cycle processes. The process of precipitation exhibits significant variability in space and time, is associated with different water phases (liquid or solid) and depends on several other factors (aerosols, orography etc), which make estimation and mod...
Presentation
First results on ORCHIDEE hydrology. Focus on the Yangtze and Yellow river basins, China.
Presentation
Full-text available
Global-scale evaluation of the hydrology simulated by the high-latitude version of ORCHIDEE (MICT)
Article
The aim of this study is to compare the surface soil moisture (SSM) retrieved from ESA's Soil Moisture and Ocean Salinity mission (SMOS) with the output of the ORCHIDEE (ORganising Carbon and Hydrology In Dynamic EcosystEm) land surface model forced with two distinct atmospheric data sets for the period 2010 to 2012. The comparison methodology is f...
Article
Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the land surface model ORCHIDEE-CAN (Organising...
Article
Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the land surface model ORCHIDEE-CAN (Organising...