Chia-Ying Tu

Model structure and land parameter identification: An inverse problem approach

[1] Model structures for the parameterization of energy and water exchanges between the atmosphere and the land are explored, and the parameters are identified. Minimizing the root-meansquare error (RMSE) of the calculated air temperature is used as the objective function. Eight parameters are determined within 14 iterations over two urban sites in a subtropical island. The identified values of these parameters can be compared with those listed in the literature. The results show that (1) a proper choice of canopy resistance is important in determining the mean temperature; (2) using a scheme to calculate stomatal resistance from vegetated areas shows improvements in simulating the diurnalvariations of the temperature, decreasing the RMSE by0.4K; (3) using a scheme to accommodate the effect of evaporation from skin reservoirs during rain events shows improvements in determining the temperature immediately after the rain, decreasing the RMSE by 0.1 K; (4) while incorporating a soil-moisture availability function does not show improvement in the model performanceunless anextra water table variable isadded, which decreases the RMSE by 0.03 K. Incorporating all of the above model structures, the calculated hourly air temperature has a correlation coefficient of as high as 0.97 with a RMSE of 1.4 K. INDEXTERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 1818 Hydrology: Evapotranspiration; 1833 Hydrology: Hydroclimatology; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; KEYWORDS: inverse problem, parameter identification, Taipei, Hualien, evapotranspiration, land surface processes

Quantification on source/receptor relationship of primary pollutants and secondary aerosols from ground sources. Part II. Model description and case study

A Circuit Trajectory transfer-coefficient model (CTx) is developed in this study based on the parameterization presentedin a companion paper (Tsuang et al., Atmos. Environ., in this issue). CTx was testedby applying it to Metropolitan Taipei for the entire year 1998. The model was calibrated in January and verified throughout the year. The results indicate that the correlation coefficients (r) for daily concentrations of CO, NOx ,S O 2 ,P M 2.5 andPM 10 were 0.75, 0.69, 0.39, 0.55 and0.55, respectively, with biases of the means ranging from 0% to 20% d uring the verification period. According to contour plots of contributed concentrations to the city, ‘‘teleconnections’’ between source emissions and their contributions to the city can be identified. In addition, the model captures most of the dust episodes except during the periods of Asian dust storms. The sensitivity analysis shows that the calculated PM10 concentration is most sensitive to its dry deposition velocity as well as its emission rate. A more thorough study on the deposition velocity of PM2.5 is suggested. r 2002 Elsevier Science Ltd. All rights reserved.

Effects of Surface Orography and Land–Sea Contrast on the Madden–Julian Oscillation in the Maritime Continent: A Numerical Study Using ECHAM5-SIT

AbstractThis study uses the atmospheric general circulation model (AGCM) ECHAM5 coupled with the newly developed Snow–Ice–Thermocline model (ECHAM5-SIT) to examine the effects of orography and land–sea contrast on the Madden–Julian oscillation (MJO) in the Maritime Continent (MC) during boreal winter. The ECHAM5-SIT is one of the few AGCMs that realistically simulate the major characteristics of the MJO. Three experiments are conducted with realistic topography, without orography, and with oceans only in the MC region to evaluate the relative effects of orography and land–sea contrast. Orography and land–sea contrast have the following effects on the MJO in the MC: 1) a larger amplitude, 2) a smaller zonal scale, 3) more realistic periodicity and stronger eastward-propagating signals, 4) a stronger southward detour during the eastward propagation, 5) a distorted coupled Kelvin–Rossby wave structure, and 6) larger low-level moisture convergence. The existence of mountainous islands also enhances the mean w...

Variability of hydrological extreme events in East Asia and their dynamical control: A comparison between observations and two high-resolution global climate models

This work investigates the variability of extreme weather events (drought spells, DS15, and daily heavy rainfall, PR99) over East Asia. It particularly focuses on the large scale atmospheric circulation associated with high levels of the occurrence of these extreme events. Two observational datasets (APHRODITE and PERSIANN) are compared with two high-resolution global climate models (HiRAM and HadGEM3-GC2) and an ensemble of other lower resolution climate models from CMIP5. We first evaluate the performance of the high resolution models. They both exhibit good skill in reproducing extreme events, especially when compared with CMIP5 results. Significant differences exist between the two observational datasets, highlighting the difficulty of having a clear estimate of extreme events. The link between the variability of the extremes and the large scale circulation is investigated, on monthly and interannual timescales, using composite and correlation analyses. Both extreme indices DS15 and PR99 are significantly linked to the low level wind intensity over East Asia, i.e. the monsoon circulation. It is also found that DS15 events are strongly linked to the surface temperature over the Siberian region and to the land-sea pressure contrast, while PR99 events are linked to the sea surface temperature anomalies over the West North Pacific. These results illustrate the importance of the monsoon circulation on extremes over East Asia. The dependencies on of the surface temperature over the continent and the sea surface temperature raise the question as to what extent they could affect the occurrence of extremes over tropical regions in future projections.