Shihua Lu

Wind-Driven South China Sea Deep Basin Warm-Core/Cool-Core Eddies

The formation of the South China Sea (SCS) deep basin warm-core and cool-core eddies was studied numerically using the Princeton Ocean Model (POM) with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography. Numerical integration was divided into pre-experimental and experimental stages. During the pre-experimental stage, we integrated the POM model for three years from zero velocity and April temperature and salinity climatological fields with climatological monthly mean wind stresses, restoring type surface salt and heat fluxes, and observational oceanic inflow/outflow at the open boundaries. During the experimental stage, we integrated the POM model for another 16 months under three different conditions: one control and two sensitivity runs (no-wind and no lateral transport). We take the fields of the last 12 months for analysis. The simulation under control run agrees well with earlier observational studies on the South China Sea surface thermal variabilities. In addition, the sensitivity study further confirms that the wind effect is the key factor for generation of the SCS deep basin warm/cool eddy and that the lateral boundary forcing is the major factor for the formation of the strong western boundary currents, especially along the southeast Chinese coast during both summer and winter monsoon seasons.

Particulate air pollution in Lanzhou China

Concentrations of total suspended particles (TSP) and PM(10) in Lanzhou China have been kept high for the past two decades. Data collected during the intensive observational period from October 1999 to April 2001 show high TSP and PM(10) concentrations. Starting from November, the PM(10) pollution intensifies, and reaches mid to high alert level of air pollution, continues until April next year, and is at low alert level in the summer. In the winter and spring, the TSP concentration is 2-10 times higher than the third-level criterion of air quality (severe pollution). Effects of intrinsic factors (sources of pollution) and remote preconditions (propagation of dust storms) for severe PM(10) and TSP pollution in Lanzhou are analyzed.

Temporal and Spatial Variabilities of Japan Sea Surface Temperature and Atmospheric Forcings

In this study, we used the National Centers for Environmental Prediction monthly sea surface temperature (SST) and surface air temperature (SAT) data during 1982–1994 and the National Center for Atmospheric Research surface wind stress curl data during 1982–1989 to investigate the Japan Sea SST temporal and spatial variabilities and their relations to atmospheric forcing. First, we found an asymmetry in the correlation coefficients between SST and wind stress curl, which implies that the SST variability at the scales of the order of one month is largely due to atmospheric forcing. Second, we performed three analyses on the data fields: annual mean, composite analysis to obtain the monthly anomaly relative to the annual mean, and empirical orthogonal function (EOF) analysis on the residue data relative to the summation of the annual mean and the monthly anomaly. The first EOF mode of SST accounts for 59.9% of the variance and represents the Subpolar Front. The temporal variation of the first EOF mode implies that the deep Japan Sea could be cooler in cold seasons (November–April) of 1984–1987. Third, we computed cross-correlation coefficients among various principal components and found that the atmospheric warming/cooling is the key factor causing intra-seasonal and interannual SST variabilities.

On Haney-type surface thermal boundary conditions for ocean circulation models

Abstract Haney-type surface thermal boundary conditions linearly connect net downward surface heat flux Q to air–sea temperature difference (gradient-type condition) ΔT1 or to climate/synoptic sea temperature difference (restoring-type condition) ΔT2 by a coupling coefficient κ. In this study, the authors used the global reanalyzed data (6-h resolution) of Q, surface air temperature TA, and sea surface temperature TO from the National Centers for Environmental Prediction during 1 October 1994–31 December 1995 to verify the validity of Haney-type surface thermal boundary conditions. First, daily means of these variables were computed to get rid of diurnal variation. Second, the cross-correlation coefficients (CCC) between Q and (ΔT1, ΔT2) were calculated. The ensemble mean CCC fields show (i) no correlation between Q and ΔT2 anywhere in the world oceans, (ii) no correlation between Q and ΔT1 in the equatorial regions, and (c) evident correlation (CCC ≥ 0.7) between Q and ΔT1 in the middle and high latitude...

A Coastal Air-Ocean Coupled System (CAOCS) Evaluated Using an Airborne Expendable Bathythermograph (AXBT) Data Set

A coastal atmosphere-ocean coupled system (CAOCS) is developed with Princeton Ocean Model (POM) as the oceanic component, and with National Center for Atmospheric Research (NCAR) regional climate model (RegCM2) as the atmospheric component. The model domain (98.84°–121.16°E, 3.06°S–25.07°N) covers the whole SCS and surrounding land and islands. The surface fluxes of water, heat (excluding solar radiation), and momentum are applied synchronously with opposite signs in the atmosphere and ocean. Flux adjustments are not used. The CAOCS model was verified using an intensive airborne expendable bathythermograph (AXBT) survey between 14–25 May 1995 over the majority of the SCS down to about 300-m depth.

Afforestation for reduction of NOX concentration in Lanzhou China

Lanzhou is one of the major industrial cities in northwest China, the capital of Gansu Province, and located at a northwest-to-southeast oriented valley basin with elevation about 1500-1600-m. Due to topographic and meteorological characteristics, Lanzhou is one of the most polluted cities in China. Meteorological conditions (low winds, stable stratification especially inversion), pollutant sources and sinks affect the air quality. Lanzhou government carried out afforestation and pollutant-source reduction (closing several heavy industrial factories) to improve the air quality for the past two decades. In this study, effect of afforestation on reducing the NO(X) concentration is investigated numerically using RAMS-HYPACT model.

An Air-Ocean Coupled Nowcast/Forecast System for the East Asian Marginal Seas

The South China Sea (SCS), Yellow/EaBt China Sea (YES), and Japan/East Sea (JES) are major east Asian marginal seas (EAMS). The complex topography includes the broad shallows of the Sunda Shelf in the south/southwest of SCSi the continental shelf of the Asian landmass in the north, extending from the Gulf of Tonkin to the YES; a deep, elliptical shaped SCS and JES basins, and numerous reef islands and underwater plateaus scattered throughout (Fig. 1a). The shelf that extends from the Gulf of Tonkin to the YES is consistently near 70 m deep, and averages 150 km in width.

Chapter 16 A numerical simulation of Japan/east sea (jes) thermohaline structure and circulation

Publisher Summary This chapter describes the Japan/East Sea (JES) current systems. The chapter discusses the depiction of the seasonal variation of atmospheric forcing, numerical ocean model and integration, and simulated seasonal variability of temperature, salinity, and circulation. The JES circulation and thermohaline structure are simulated using Princeton Ocean Model (POM) with seasonal surface flux forcing. Two steps are used to initialize POM. During the first step POM is integrated for two years from zero velocity, and the January climatological temperature and salinity fields with climatological monthly mean surface wind stress. The final states of the restoring run are taken as initial conditions for the second step. During the simulation run, POM is integrated again for two more years with climatological monthly mean surface wind stress, net heat flux, and freshwater flux from the Comprehensive Ocean-Atmosphere Data Set (COADS) data. POM simulates the formation of the Japan/East Sea Sub-Polar Front (JES SPF) and its seasonal variation. The simulated thermal field shows a strong north-south thermal asymmetry across the SPF.