NCEP EMC (IMSG), 2004.09 ~ 2018.01

1. Acted as the Global Modeling Task Leader of NCEP-EMC contractors employed by IMSG, Inc. Led the task of NCEP/EMC global NWP model verification and evaluation. Spearheaded multiple innovative NWP model verification and evaluation projects.

2. Developed a Global NWP Model Verification System. This system contains verification of forecast skill scores and evaluation of weather-sensible elements such as precipitation, hurricane track and intensity and surface temperature etc. The system has been widely used by NWP model developers at NCEP/EMC, JCSDA, NOAA/ESRL, a few universities and a few international NWP centers. It has also been used at EMC for monitoring operational GFS performance and for comparing GFS with other international NWP models (see http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/).

3. Collected and processed daily NWP forecasts data from major international forecast centers. Carried out routine model verification jobs. Provided monthly and yearly summaries of GFS performance for NWS management and community users.

4. Acted as the designated personnel at NCEP EMC to execute global GFS parallel experiments for testing and implementation. Worked together with a core group of GFS developers to maintain the GFS parallel system. Helped branch members to execute experiments and perform forecast verifications.

5. Made major contributions to the Q3FY2010 T574L64 GFS implementation and the upcoming Q1FY2015 T1534L64 Semi-Lagrangian GFS implementation. Performed multiple sets of experiments to tune and evaluate the models. Prepared implementation request documents, and worked closely with NCEP NCO staff to diagnose and solve problems identified in the process of implementation for production.

6. Developed a positive-definite tracer transport scheme in the vertical for the NCEP GFS. This scheme solved a longstanding problem in the GFS, that is, the GFS old transport scheme tends to produce negative tracers, including water vapor and cloud water, in the upper atmosphere. Also developed a new scheme to parameterize the dependence of surface albedo on solar zenith angle. Both schemes were included in the Q3FY2010 GFS implementation.

7. Performed diagnosis and sensitivity experiments to evaluate new modules of model physics and dynamics. Compared GFS clouds with satellite products, such as CLAVR-x and GSIP to quantify GFS's deficiency in cloud modeling.

8. Developed a Monte Carlo significance test tool for evaluating precipitation skill scores, an RMSE decomposition algorithm for isolating mean errors from pattern errors, and coded numerous model verification programs.

9. Carried out data denial experiments for the JPSS project and Hurricane Sandy project.

NASA/GSFC, 2002.12 ~ 2004.08

1. Investigated the trend and variability of East Asian precipitation and its association with SSTs. publication

2. Developed a multi-year mixed-layer ocean model based on the theoretical framework of Gaspar (1988), and couple it to the DAO fvGCM and NSIPP GCM. The coupled model will be used to study the relation between southeast Asian balck carbon and monsoonal rainfall.

3. Assessed the potential predictability of surface-air temperature and precipitation over the United States using a GCM forced by "perfect" soil-moisture, which was obtained by assimilating the observed GPCP precipitation. It was found that the predictability of US surface-air temperature and precipitation in boreal late spring and summer was greatly enhanced. The results provide an estimate for the limits of potential predictability if soil-moisture variability is to be perfectly predicted publication (highlighted by BAMS in 2004)

NCEP, 2000.1 ~ 2002.11

1. Participated in the development of the then-CPC Climate Modeling Branch Coupled Model Prediction system for dynamical ENSO forecast. For instance, I used the SVD statistical tool to minimize the errors of surface wind stresses in the coupled system during interactive model integrations.

2. Diagnosed the relationships among SST, surface wind stress and precipitation in the tropical Pacific using both observations, NCEP and ECMWF reanalyses and model simulations. publication

3. Investigated the impact of snow variability on the response of North American surface air temperature to ENSO. It is found that the surface climate anomalies related to ENSO are greatly enhanced by a local snow-albedo feedback. This feedback mechanism has significant implications for seasonal climate predictions and greenhouse gas-induced climate changes. publication

4. Investigated the intensity of hydrological cycles in warmer climates when CO2 doubles. Both AGCM and coupled AGCM mixed-layer ocean models were used. We found that precipitation may not necessarily increase in warmer climates if the climate sensitivity of a GCM is small. This work was cited by the IPCC report and many colleagues. publication

5. Investigated the trends in precipitation and surface air temperature over the tropical land and ocean in both observations and GCM simulations. It was found that in the past 50 years while temperature has been increasing over both the land and ocean, only over the ocean has precipitation been increasing. Land precipitation has been decreasing. This work was cited by the IPCC report. publications

6. Compared the influences of snow and SST variability on extratropical climate in northern winter in a set of AMIP-type GCM simulations. It was found that the influence of snow variability is confined to the lower troposphere, while the largest influence of tropical SST variability on the extratropical flow occurs in the upper troposphere. The impact of snow is related to the dependence of surface albedo on snow depth. publication

7. Implemented the CHOU longwave radiation package in the then-CPC operational seasonal forecast model (GSM). Introduced Slingo's scheme to the GSM for diagnostically predicting stratiform clouds.

UIUC, 1994.8 ~ 1999.12

Development of Numerical Models

1. UIUC 24-Layer Stratosphere/Troposphere General Circulation Model (24-L ST-GCM)

The construction of the UIUC 24-L ST-GCM, which extends up to 1 hPa, began in 1994. It was based primarily on the UIUC 7-layer troposphere GCM and 11-layer troposphere/lower-stratosphere GCM . I replaced the model’s terrestrial and solar radiation routines, revised the interaction between clouds and radiation, included in the model both the direct and indirect radiative forcing of sulfate aerosol, and added a parameterization for orographically excited subgrid-scale gravity-wave drag. publication
2. Other Atmospheric GCMs

Developed a 40-layer atmospheric GCM with its top at 98km based on the 24-L ST-GCM to explore the influences of model top, sponge-layer friction and subgrid-scale gravity-wave drag on the simulation of Northern-Hemisphere polar-night jet. I also updated the radiation routines and radiation-cloud interaction of the UIUC 11-layer AGCM. A manuscript, which investigates the effect of Alexander-Dunkerton gravity-wave parameterization on upper atmospheric temperature and circulation, has been submitted to JGR
3. One-Dimensional Radiative-Convective Models (1-D RCM)

Developed a set of 1-D RCMs with different vertical representations. These RCMs use the radiation routines of the UIUC 24-L ST-GCM and Manabe’s surface convection. Simple cloud-radiation interaction modules were implemented. I, as well as other members in the UIUC Climate Research Group, used these RCMs to examine climate feedback, climate sensitivity and radiative forcing of greenhouse gases, clouds and aerosols.
4. A Mie-Scattering Model

Coded a Mie scattering model to calculate the optical properties of sulfate aerosol, which are being used in above-mentioned RCMs and atmospheric GCMs.
5. Coupling of Atmospheric and Oceanic GCMs

Coupled the UIUC 18-layer oceanic GCM with the 24-L ST-GCM and performed a set of coupling simulations.

Researches Performed Other than My Ph.D. Dissertation

1. Simulation and Analysis of Climate and Climate Changes

Performed and analyzed more than ten equilibrium climate simulations using the UIUC 11-layer atmosphere/mixed-layer-ocean model. They are, for example, eight simulations forced by direct radiative forcing of tropospheric sulfate aerosol with either global or regional emissions of sulfur dioxide from either natural or anthropogenic sources, one simulation with 2% increase of solar constant; and one with perturbed tropospheric ozone concentration. For each experiment, radiative forcing was calculated off-line. Climate changes and climate sensitivity were examined. Some results have been used to construct geographical scenarios of future climate changes by Dr. Schlesinger et al. [1998] and to perform integrated climate modeling by climate impact analysts .
2. The Second Atmospheric Model Intercomparison Project (AMIP-II)

Modified the UIUC 24-L ST-GCM following AMIP-II’s guidelines and performed a 17-year transient climate simulation for this project.
3. Studies on the Uncertainty of Direct Radiative Forcing of Sulfate Aerosol.

Using the Mie scattering model and a 26-layer RCM, calculated and tested the dependence of sulfate aerosol optical properties on aerosol particle radius, size distribution and refractive index; examined the dependence of radiative forcing of sulfate aerosol on aerosol particle radius, optical depth, surface albedo and solar zenith angle. Part of the results was contributed to an intercomparison project and published in JGR. publication
4. Cooperation with Co-workers

a). Study radiative forcing of historical volcanic eruptions (Dr. N. Andronova); b). Develop off-line and on-line couplings of the 24-L ST-GCM with an atmospheric chemical-transport model (Dr. E. Rozanov); c). Investigate climate sensitivity and climate feedback (Dr. M. E. Schlesinger); d). Estimate the uncertainty of the direct radiative forcing by anthropogenic sulfate aerosol using a combinatorial method (Dr. A. Omar); e). Participated in an intercomparison project, Threshold Sea Surface Temperature for Convection, coordinated by Dr. D. Randall in Colorado State University.