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Cai J.,Nanjing University of Information Science and Technology | Cai J.,George Mason University | Xu J.,George Mason University | Powell A.M.,The Center for Satellite Applications and Research | And 2 more authors.
Theoretical and Applied Climatology

Based on the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis temperature dataset in the period of 1948–2014, the temperature contrast between the Arctic and equator in the pre- and post periods of the 1976/1977 regime shift is compared. An index measuring the temperature contrast is defined as the difference between the Arctic zone (70° N–90° N) and the equatorial region (10° S–10° N). The variations of the temperature contrast can be mainly explained by the local sea ice variations through sea ice–albedo–temperature feedback before 1976/1977 and the energy transportation to the Arctic together with the local sea ice after 1976/1977. The impacts of the Arctic minus equator (AmE) temperature contrast on the high-level westerly jet, and the polar easterlies show a significant difference during the two periods. A strong temperature anomaly associated with the temperature contrast in the two periods is found in the high latitude, but different patterns are observed at the high and low levels. The correlated water vapor appeared in the Indian Ocean and Maritime Continent before 1976/1977 and moved to northeastern Canada and eastern North America after 1976/1977. © 2015 Springer-Verlag Wien Source

He X.,State Oceanic Administration | He X.,Zhejiang University | Bai Y.,State Oceanic Administration | Pan D.,State Oceanic Administration | And 6 more authors.
Remote Sensing of Environment

Total suspended particulate matter (TSM) in coastal waters is often characterized by high concentration and significant diurnal dynamics. Insufficient spatial and temporal resolution limits both cruise sampling and polar-orbiting satellite remote sensing in the mapping of TSM diurnal dynamics in coastal regions. However, the in-orbit operation of the world's first geostationary satellite ocean color sensor, GOCI, provides hourly observations of the covered area. In this study, we proposed a practical atmospheric correction algorithm for GOCI data in turbid waters. The validation results showed that the GOCI-retrieved normalized water-leaving radiances matched the in situ values well in both quantity and spectral shapes. We also developed a regional empirical TSM algorithm for GOCI data that is applicable in extremely turbid waters. Based on these atmospheric correction and regional TSM algorithms, we generated hourly TSM maps from GOCI Level-1B data. The diurnal variations derived by GOCI were a good match to the buoy data. The hourly GOCI observations revealed that various regions and tidal phases had different diurnal variation magnitudes, with a maximum of up to 5000. mg/l in central Hangzhou Bay. Strong wind events, such as typhoons, can significantly increase TSM in the bay; however, both the GOCI observations and buoy measurements indicated that this increase was episodic, had a short duration, and returned to normal within a day after the passage of a typhoon. Our results suggest that GOCI can successfully map the diurnal dynamics of TSM in turbid coastal waters. Moreover, the significant diurnal dynamics revealed in the hourly GOCI observations implied that caution should be taken in mapping TSM in coastal waters using cruise sampling and conventional polar-orbiting satellite data, as the temporal resolution is insufficient for catching diurnal variations. © 2013 Elsevier Inc. Source

Kang H.-Q.,Nanjing University of Information Science and Technology | Zhu B.,Nanjing University of Information Science and Technology | Zhu T.,Colorado State University | Zhu T.,College Park | And 2 more authors.
Boundary-Layer Meteorology

The impact of upstream urbanization on the enhanced urban heat-island (UHI) effects between Shanghai and Kunshan is investigated by analyzing seven years of surface observations and results from mesoscale model simulations. The observational analysis indicates that, under easterly and westerly winds, the temperature difference between Shanghai and Kunshan increases with wind speed when the wind speed <5 m s-1. The Weather Research and Forecasting (WRF) numerical model, coupled with a one-layer urban canopy model (UCM), is used to examine the UHI structure and upstream effects by replacing the urban surface of Shanghai and/or Kunshan with cropland. The WRF/UCM modelling system is capable of reproducing the surface temperature and wind field reasonably well. The simulated urban canopy wind speed is a better representation of the near-surface wind speed than is the 10-m wind speed at the centre of Shanghai. Without the urban landscape of Shanghai, the surface air temperature over downstream Kunshan would decrease by 0.2-0.4° C in the afternoon and 0.4-0.6° C in the evening. In the simulation with the urban landscape of Shanghai, a shallow cold layer is found above the UHI, with a minimum temperature of about -0.2 to-0.5°C during the afternoon hours. Strong horizontal divergence is found in this cold layer. The easterly breeze over Shanghai is strengthened at the surface by strong UHI effects, but weakened at upper levels. With the appearance of the urban landscape specific humidity decreases by 0.5-1 g kg-1 within the urban area because of the waterproof property of an urban surface. On the other hand, the upper-level specific humidity is increased because of water vapour transferred by the strong upward vertical motions. © 2014 Springer Science+Business Media Dordrecht. Source

Huang N.,Shanghai Marine Meteorological Center | Fang Z.,Nanjing University | Liu F.,Shanghai Marine Meteorological Center
Advances in Meteorology

The buoy observation network in the East China Sea is used to assist the determination of the characteristics of tropical cyclone structure in August 2012. When super typhoon "Haikui" made landfall in northern Zhejiang province, it passed over three buoys, the East China Sea Buoy, the Sea Reef Buoy, and the Channel Buoy, which were located within the radii of the 13.9 m/s winds, 24.5 m/s winds, and 24.5 m/s winds, respectively. These buoy observations verified the accuracy of typhoon intensity determined by China Meteorological Administration (CMA). The East China Sea Buoy had closely observed typhoons "Bolaven" and "Tembin," which provided real-time guidance for forecasters to better understand the typhoon structure and were also used to quantify the air-sea interface heat exchange during the passage of the storm. The buoy-measured wind and pressure time series were also used to correct the intensity of "Damrey" initially determined by CMA. © 2013 Ningli Huang et al. Source

Xu J.,Shanghai Marine Meteorological Center | Guo J.,Fengxian District Meteorological Office of Shanghai Municipaltity | Huang N.,Shanghai Marine Meteorological Center
Journal of Natural Disasters

NCEP objective reanalysis data was used to diagnose the path and intensity of No. 1215 typhoon "Bolaven" from the situation field at 500 hPa, the location and intensity changes of the subtropical high, the low-level flow field, the horizontal distribution of the water vapor flux and the water vapor flux divergence, the vertical velocity distribution and the structural characteristics of the heart-warming. Meanwhile, the observations of the East China Sea buoys and reef buoy, the observed SST and vertical wind shear were shown. By the above diagnostic analysis, it is found that the northward and eastward jump of the subtropical high led to the path of "Bolaven" folding northward twice. When "Bolaven" move northward, both moisture conditions and strength are weakened, because Tembin blocked part of the transportation of the water vapor from the low-latitude ocean. It cause the asymmetric characteristics of water vapor flux and water vapor flux divergence of " Bolaven", which made west part dry and east part wet. The gradual increases of vertical wind shear from south to north over East China Sea weakened the typhoon "Bolaven". The intrusion of the cold and dry air from the northwest area and the northwest-southeast distribution characteristics of the sea surface temperature gradient at East China Sea made the the structural characteristics of the typhoon east part strong and west part weak. All these reasons results in the insignificant precipitation when "Bolaven" went through the same latitude of Shanghai. Source

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