Fei Chen

Scientist III
TIIMES - RAL
WCAS & BEACHON

Contact Information:
PO Box 3000, Boulder, CO 80307-3000
Office: FL2-3023
Telephone: 303-497-8454
Email: feichen@ucar.edu

Project Summary:

Investigating land atmosphere interactions and their impacts on diurnal cycle of PBL and Precipitation

Fei Chen, Margaret LeMone, Stan Trier , Mukul Tewari

Collaborators:  D. Niyogi, Anil Kumar, and Joe Alfieri (Purdue) J. Basara (OU), P. Blanken and Eric Small (CU), R. Cuenca (Oreg. State Univ.), Venkat Lakshmi (U South Carolina), K. Michell and Mike Ek (NCEP), C. Peter-Lidards (GSFC), F. Couvreux (Meteo-France, France), S. Bastin (CNRS, France).

The overall goals of our work is to utilize offline land surface models, coupled WRF/Noah model, and IHOP_2002 field observations to improve our understanding of surface water cycle and atmospheric boundary layer processes, and to improve the representation of those processes in coupled numerical models. Our major focus of FY07 for the Water Cycle Program has been to:

• Continue updating the RAL website hosting the IHOP_2002 surface, soil and vegetation data, and aircraft data.
• Utilize these data to study the relationship of surface heat fluxes to vegetation.
• Use IHOP_2002 data and other field data to evaluate and improve the Noah land surface model.
• Continue analyzing land surface effects on PBL properties and precipitation in 12-day WRF-model simulations of an episode of heavy rainfall during IHOP_2002.

FY07 Summary

Surface heterogeneity in surface sensible and latent heat fluxes, soil moisture and vegetation

The HRLDAS does not seem to replicate observed horizontal variability for 29 May 2002, one of the days in IHOP_2002 with the most surface variability due to a heavy rain event occurred two days earlier. Updating land-use data using MODIS and parameter table in Noah to reflect changes since the default land use was defined in HRLDAS didn’t help. A number of HRLDAS simulations were conducted and we found two major factors contributing to HRLDAS’s failure to capture small-scale heterogeneity: 1) too uniform soil moisture due to inadequate rainfall input data, and 2) a wrong constant in the Zilitenkevich equation relating the roughness lengths for momentum and heat in the surface parameterization scheme used in HRLDAS. A value of 0.5 for this constant produces the most successful simulation for this case. Results are summarized in LeMone et al. (2007) submitted to Monthly Weather Review.

A number of analyses were conducted using IHOP_2002 surface and King Air aircraft data and revealed a strong relationship of sensible and latent heat fluxes (H and LE) to both vegetation and soil moisture (LeMone et al. 2007, Alfieri et al. 2007, LeMone et al. 2007). Results based on IHOP_2002 data and model simulations pointed out that the boundary-layer water-vapor distribution is controlled by both advection and surface processes, and vegetation and soil moisture gradients play an important role in determining local gradients (Couvreux et al. 2007).

Using MODIS remote-sensing data to improve the canopy resistance scheme in Noah

The goal of this investigation is to synthesize and integrate recent remotely- sensed and in-situ datasets and products to systematically evaluate and improve the representation of vegetation and transpiration processes in the Noah LSM, for use in both an uncoupled land data assimilation system (LDAS) and a coupled Weather Research and Forecast (WRF) numerical prediction model. Recent multi-month tests at NCEP showed that modulating Rc substantially altered the NCEP Global Forecast System (GFS) and Nested Mesoscale Model (NMM), both using the Noah LSM, realtime forecast. Therefore, this project is in response to the emerging need posed by the NCEP land surface modeling community and the operational forecasting community. The project will take advantage of and build upon the recent calibration and testing of canopy resistance (Rc) parameters undertaken at NCEP for improving the operational model performance, and upon the availability of new satellite products and in-situ field datasets.

Results from HRLDAS simulations for 2001-2002 incorporating Niyogi’s GEM model for Rc calculation are analyzed and evaluated against IHOP_2002 and Oklahoma Mesonet data. Major findings are below, the results are summarized in a manuscript by Kumar et al. (2007) in preparation.

• Responses of Rc to environmental and soil conditions are fairly different in Jarvis and GEM formulations
• That leads to large differences in soil moisture and latent heat fluxes (especially for evergreen forest and grassland)
• Incorporation of GEM in Noah is sensitive to description of land use (C3, C4 grass) vegetation phenology (LAI, vegetation fraction, etc). Need to develop C3, C4 or mosaic representation
• Noah-GEM produces better latent heat flux and soil moisture.

Click on picture to view the entire figure   The boundary-layer portion of the International H2O Experiment (IHOP_2002) supports its overall goal to improve convective precipitation prediction through better use and representation of water vapor in numerical weather prediction (NWP) models through estimating surface water vapor and sensible heat fluxes, characterizing the influence of surface properties on boundary-layer heterogeneity, and understanding the role that these play in the initiation and evolution of convective precipitation systems. Data collection and analysis were designed to provide benchmarks to enable improvements in the representation of land-surface and boundary-layer processes in NWP models.

Analysis of land surface effects on PBL properties and precipitation in 12-day WRF-model simulations of an episode of heavy rainfall during IHOP_2002.

We have investigated the reasons for PBL and precipitation differences between two convection-resolving simulations of a 12-day warm season convection period over the central United States. These two simulations used different initial soil wetness conditions and different LSMs coupled with the WRF atmospheric model: 1) the control simulation (HRLDAS1) used HRLDAS produced date specific initial land state and the Noah LSM, and 2) the other simulation (SLAB1) used a lower-resolution climatology soil wetness and the less sophisticated SLAB LSM. The differences in land surface initial condition are particularly significant because of a large soil moisture anomaly during the period of study with drier than normal conditions over the Rocky Mountain region and adjacent high plains and slightly wetter than normal conditions over parts of the Midwest. Comparison of simulated near surface thermodynamic variables with observations revealed a much more accurate simulation with HRLDAS1 than with SLAB1.

Results suggest that the choice of LSM (Noah or the less sophisticated SLAB model) significantly influences the diurnal cycle of near-surface potential temperature and water vapor mixing ratio. However, the initial soil wetness also has a major impact on these thermodynamic variables, particularly during and immediately following the most intense phase of daytime surface heating. The land-surface condition influences the daytime PBL evolution through both local and upstream surface evaporation and sensible heat fluxes, and through differences in the mesoscale vertical circulation that develops in response to horizontal gradients of the latter. Resulting differences in late afternoon PBL moist static energy and stability near the PBL top are associated with differences in subsequent late afternoon and evening precipitation in locations where the initial soil wetness differs among simulations.

The current work also suggests a connection between soil wetness and its horizontal gradients, the afternoon PBL, and subsequent evening precipitation over specific mesoscale regions. Systematic differences in regional precipitation frequencies are found among the simulations. However, no single simulation most accurately reproduces the observed diurnal cycle of precipitation at all times over both regions . Aspects of this work were presented at the AMS Conference on Hydrology. A journal article (Trier et al. 2007) has been written and submitted. Peer reviews have been received and the article is currently being revised.

Presentations:

• Climate model uncertainty in forecasting precipitation at continental scales: A comparison of models results and data., Other, Boulder USA, October 07
• Developing an integrated urban modeling system in WRF: current status and future plan., S&T, Exeter GBR, October 07
• Uncertain in forecasting precipitation by climate and weather models at continental scales., S&T, Hong Kong CHN, October 07
• Effects of using high-resolution urban land-use and building morphological data seets on the WRF/urban coupled model simulations for the Houston-Galveston areas, S&T, Chapel Hill USA, October 07

TIIMES External Collaborators:

Jeffrey Basara, University of Oklahoma
Peter Blanken, University of Colorado
Richard Cuenca, Oregon State University
Michael Ek, National Centers for Environmental Prediction - NOAA
John Eylander, Air Force Weather
Alex Lau, Hong Kong University of Science & Technology
Ken Mitchell, National Centers for Environmental Prediction - NOAA
Dev Nyogi, Purdue University
Christa Peters-Lidard, Goddard Space Flight Center (GSFC) - NASA
Eric Small, University of Colorado

Publications:

Gochis, D. J., G. Bonan, E. Brandes, F. Chen, D. Lenschow, M. LeMone, R. Rasmussen, T. T. Warner, M. Ek, K. Mitchell, 2007: A ten-year vision for advancing coupled land-atmosphere prediction. Water Resources Research. (Submitted)

LeMone, M., M. Tewari, F. Chen, J. G. Alfieri, D. Niyogi, 2007: Adding horizontal heterogeneity as a criterion for evaluating a land-surface model. Mon. Wea. Rev.. (Submitted)

Alfieri, J. G., D. Niyogi, M. A. LeMone, F. Chen, S. Fall, 2007: A simple reclassification method for correcting uncertainty in land use/land cover datasets used with land surface models. Pure Appl. Geophys., 164, 1789-1809, doi: 10.1007/s00024-007-0241-4.

Trier, S. B., F. Chen, K. W. Manning, M. A. Lemone, C. A. Davis, 2007: Sensitivity of the PBL and precipitation in 12-day simulations of warm-season convection using different land surface models and soil wetness conditions. Mon. Wea. Rev.. (Submitted)

Chen, F., K. W. Manning, M. A. LeMone, S. B. Trier, J. G. Alfieri, R. Roberts, M. Tewari, D. Niyogi, T. W. Horst, S. P. Oncley, J. B. Basara, P. D. Blanken, 2007: Description and evaluation of the characteristics of the NCAR high-resolution land data assimilation system. J. Appl. Meteor. Climat., 46, 694-713, doi: 10.1175/JAM2463.1.

Alfieri, J., X. Xiao, D. Niyogi, R. A. Pielke, Sr., F. Chen, M. A. Lemone, 2007: Satellite-based modeling of transpiration and evaporation of grasslands and croplands in the Southern Great Plains, USA. Global Planetary Changes. (Submitted)

LeMone, M. A., F. Chen, J. G. Alfieri, M. Tewari, B. Geerts, Q. Miao, R. L. Grossman, R. L. Coulter, 2007: Influence of land cover and soil moisture on the horizontal distribution of sensible and latent heat fluxes in southeast Kansas during IHOP_2002 and CASES-97. J. Hydrometeorol., 8, 68-87, doi: 10.1175/JHM554.1.

LeMone, M. A., F. Chen, J. Alfieri, R. Cuenca, Y. Hagimoto, P. Blanken, D. Niyogi, S. Kang, K. Davis, R. Grossman, 2007: NCAR/CU surface, soil, and vegetation observation network during the IHOP_2002 field campaign. Bull. Amer. Meteor. Soc., 88, 65-81.

Niyogi, D., H. I. Chang, F. Chen, L. Gu, A. Kumar, S. Menon, R. A. Pielke, Sr., 2007: Potential impacts of aerosol-land-atmosphere interactions on the Indian monsoonal rainfall characteristics. Natural Hazards, doi: 10.1007/s11069-006-9085-y. (In Press)

Lo, J. C. F., A. K. H. Lau, F. Chen, J. C. H. Fung, K. K. M. Leung, 2007: Urban modification in a mesoscale model and the effects on the local circulation in the Pearl River Delta region. J. Appl. Meteor. Climat., 46, 457-476.

Niyogi, D., K. Alapaty, S. Raman and F. Chen, 2006: Development and evaluation of a coupled photosynthesis - based gas exchange evapotranspiration model (GEM). J Appli. Meteorol. Climatol., submitted.

Alapaty K., D. Niyogi, F. Chen, P. Pyle, A. Chandrasekar, N. Seaman, 2007: Development of the Flux-Adjusting Surface Data Assimilation System for Mesoscale Models. J. Appl. Meteorol. Clim., in revision.

Pyle P., D. Niyogi, S. P. Arya, M. Shepherd, F. Chen, B. Wolfe, 2007: An Observational and Modeling-based Storm Climatology Assessment for the Indianapolis, urban region. J. Appl. Meteorol. and Clim., submitted.

Couvreux, F., F. Guichard, P. Austino, and F. Chen, 2007: Nature of the mesoscale boundary-layer height and water-vapor variability observed the 14 June 2002 during the IHOP 2002 campaign. Mon. Wea. Rev., submitted.