Satellite observations reveal that an ocean cooling event happened along the Yellow Sea coast of China intermittently in spring 2008, which lasted for days. During this period, the sea surface temperature (SST) dropped 3 °C-4 °C and the chlorophyll A (Chl-a) content increased by 0.5-1 mg/m3, as determined from satellite-derived products. The cold water also suppressed the sea surface capillary waves and made the ocean surface smooth, a distinct feature shown as dark patches observed in the synthetic aperture radar image acquired during this period of time. The surface wind direction varied between alongshore and offshore. We implemented an interactively coupled ocean (regional ocean modeling system) and atmosphere (Weather Research and Forecasting model) model to capture the dynamical processes of this seemingly wind-driven cooling event. When the wind changed direction such that the alongshore component blew with the land on its left side, stronger upwelling occurred; and when the wind blew offshore with no alongshore component, the upwelling still occurred in this area, but with less strength. Two simulations with idealized alongshore and offshore winds show that the upwelling can be set up within several hours. The alongshore wind is more effective than the offshore wind in transporting upper level water offshore and triggering upwelling and causing SST cooling areas that are relatively large in size, although the maximum SST cooling they cause is on the same order of magnitude.

Two satellite synthetic aperture radar (SAR) observations of the fetch in the Bohai Sea of China are presented. The sea surface winds derived from SAR data indicated a high wind of 15-16 m/s that occurred in the fetch zone. The winds are shown to have immediate direct mechanical forcing impacts on the significant wave heights (Hs) of ocean surface gravity waves. Buoy measurements and numerical wave modeling results show that the Hs increased to a maximum of 3.5 m in the semienclosed sea, 3 h after the passage of the fetch winds, and the high Hs in the sea was sustained for a total of 6 h. The Weather Research and Forecasting (WRF) model implemented in our modeling simulation captured the wind field responsible for the evolution of the fetch event. The model-simulated surface horizontal winds agree with the SAR-derived winds. In addition, the vertical wind distribution reveals that the fetch wind field reached the 800 hPa level, and the event lasted less than one day. This study demonstrates the synergy of using SAR imagery and the WRF model as effective tools to investigate the lateral and vertical structures of coastal wind.

SST cooling episodes in the early Spring are often observed by various remote sensing measurement systems near the coast of Qingdao, a city in China's Shandong province (Figure 1). Several wind-SST interaction mechanisms that can cause colder deep water to force its way upward and drive away and subsequently replace the warmer surface water, also known as upwelling, have been previously documented. Most of the previous coastal upwelling work has been focused on the mechanism of upwelling processes on a large scale and caused by winds blowing parallel to the coast and Ekman transport. Upwelling on small local scales such as the one shown in Figure 1 has not been extensively studied. However, on a more local and smaller scale, not associated with Coriolis force or Ekman transport, winds blowing offshore can also push water mechanically away from land to produce upper level divergence and upwelling. But it is not clear if the recurring upwelling in Figure 1 can be attributed to the along-coast winds or the offshore winds or the local bathymetry, or a combination of several factors. We will look into the possible mechanisms.

In this study, an atmospheric phenomenon, land breeze system, was observed on one image mode high resolution SAR image and one middle resolution optical image. WRF model was implemented with actual meteorological conditions as inputs to successfully simulate this process with some understandable discrepancies. The overpass time of ASAR and MODIS are at 10:35 AM and 11:10 AM local time in Hainan. Long time in-situ observations show that the land breeze process is converting to sea process between 10:00 AM and 12:00 AM. Thus, the satellite observed land breeze front is at its ending stage. That is one possible reason that land breeze front on ASAR image is clearer than on MODIS image. It also explained why the cloud line in MODIS image cannot maintain its shape and started to dissipate. The MODIS image also shows that the land breeze dissipation process is not spatial uniform along the whole land-sea breeze front.

NASA Soil Moisture Active/Passive (SMAP) satellite was launched on January 31st, 2015 and has been providing global soil moisture (SM) data products since April 2015. One of the primary justifications of the mission was to improve numerical weather predictions. With the SMAP SM data becoming available, it is anxiously expected that SMAP SM data could be demonstrated to significantly improve weather forecasts from numerical weather prediction (NWP) models. In this study, the NOAA Global Forecast System (GFS) and NASA Unified Weather Research and Forecast (NUWRF) model coupled with NASA Land Information System are used to carry out the demonstration. A hardwired Ensemble Kalman filter is implemented within GFS to assimilate surface SM observations. For assimilating SM data into NUWRF model, NASA Land Information System (LIS) is coupled with the NUWRF model. In this paper preliminary results of SMAP soil moisture impact on GFS and NUWRF forecasts are presented after the assimilation algorithms and system designs are introduced. Plans for more comprehensive assessment of the satellite soil moisture data impact on NWP models will be discussed.

In this paper, we present the synthetic aperture radar (SAR) observation of the detailed sea surface wind patterns associated with fetch in the Bohai Sea, China. We then implemented the WRF model to simulate the entire processes of this weather event. WRF model results show the dynamics and evolution of this event.

Synthetic aperture radar (SAR) images reveal the surface imprints of atmospheric occluded fronts. An occluded front is characterized as a low-wind zone located between and within two zones of higher winds blowing in the opposite directions on the left and right sides of the occluded front. A group of four SAR images reveal that the width of an individual occluded frontal zone and the wind magnitudes outside fronts vary greatly from case to case. In this paper, we performed a case study to analyze an occluded front observed by an Environmental Satellite (Envisat) Advanced SAR and ASCAT scatterometer along the west coast of Canada on November 24, 2011. The two-way interactive, triply nested grid (9-3-1 km) Weather Research and Forecasting (WRF) model was utilized to simulate the evolution of the occluded front. The occluded front moved toward the east during a 24-h model simulation, and the movement between 18:00 and 21:00 UTC matched the occluded front positions derived from the concurrently collected surface weather maps; from the National Oceanic and Atmospheric National Weather Service archives. The WRF-simulated low-wind zone associated with the occluded front and ocean surface wind speed match well with the SAR and scatterometer wind retrievals. High wind outside the front zone became weaker during the front evolution, whereas the width of the occluded frontal zone was contracted laterally. Analysis of the WRF model derived potential temperature field suggests that the occlusion process occurred below the 800-mb level. The structure of the occluded front studied here not only follows the conventional conceptual model and also supports the findings of a novel wrap-up conceptual model for an atmospheric frontal occlusion process.

Marine atmospheric boundary phenomena, i.e., atmospheric gravity waves (AGW), vortex streets and boundary rolls, modulate the surface wind field and will leave imprints visible on synthetic aperture radar (SAR) images. In this case study, we present an ENVISAT SAR observation of AGW offshore of the mountain Laoshan along the yellow sea coast of China. The Weather Research and Forecasting (WRF) weather model is used to simulate the development of this group of AGW. The model simulation and SAR observation agree reasonable well.

In this study, the sea surface imprints of strong mountain katabatic winds and gap winds are observed on RADARSAT-1 synthetic aperture radar (SAR) ScanSAR wide images off the west coast of the U.S. and in the Gulf of Alaska. Two case studies are presented. In the first case study, a RARASAT-1 SAR scene taken at 14:25:30 UTC on January 21, 2003 shows a finger-like wind pattern that mirrors the coastal mountain height. In the second case, the SAR image was taken at 4:41:45 UTC on December 22, 1999. It shows a strong gap wind and vortex streets through the Aleutian Islands. In order to understand the dynamics of these wind patterns observed in the SAR images, we simulated the low level atmospheric circulation using the fifth-generation Pennsylvania State University (PSU)-National Center for Atmospheric Research (NCAR) Mesoscale Model, MM5. A triple nested-grid (9/3/1 km) technique is employed to achieve a multi-scale simulation. In general the MM5 model captures the wind pattern very well and reveals the dynamics of these meso-scale atmospheric phenomena. However, the MM5 did not resolve the vortex shedding due to the model resolution and the complex nature of this phenomenon