Juan Carlos Jusem

A Cross-calibrated, Multiplatform Ocean Surface Wind Velocity Product for Meteorological and Oceanographic Applications

Abstract The ocean surface wind mediates exchanges between the ocean and the atmosphere. These air–sea exchange processes are critical for understanding and predicting atmosphere, ocean, and wave phenomena on many time and space scales. A cross-calibrated multiplatform (CCMP) long-term data record of satellite ocean surface winds is available from 1987 to 2008 with planned extensions through 2012. A variational analysis method (VAM) is used to combine surface wind data derived from conventional and in situ sources and multiple satellites into a consistent nearglobal analysis at 25-km resolution, every 6 h. The input data are cross-calibrated wind speeds derived from the Special Sensor Microwave Imager (SSM/I; F08–F15), the Tropical Rainfall Measuring Mission Microwave Imager (TMI), and the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E), and wind vectors from SeaWinds on the NASA Quick Scatterometer (QuikSCAT) and on the second Japanese Advanced Earth Observing Satellite (ADEOS-...

A multiyear global surface wind velocity dataset using SSM/I wind observations

The Special Sensor Microwave Imagers (SSM/I) aboard three DMSP satellites have improved a large dataset of surface wind speeds over the global oceans from July 1987 to the present. These data are characterized by high resolution, coverage, and accuracy, but their application has been limited by the lack of directional information. In an effort to extend the applicability of these data , methodology has been developed to assign directions to the SSM/I wind speeds and to produce analyses using these data. Following extensive testing, this methodology has been used to generate a seven and one-half year dataset (from July 1987 through December 1994) of global SSM/I wind vectors. These data are currently being used in a variety of atmospheric and oceanic applications and are available to interested investigators. Recent results presented in this paper show the accuracy of the SSM/I wind velocities, the ability of these data to improve surface wind analyses, and the propagation of a synoptic-scale convergent cortex in the Tropics that can be tracked from year to year in annual mean SSM/I wind fields. 11 refs., 5 figs., 2 tabs.

The effects of marine winds from scatterometer data on weather analysis and forecasting

Abstract Satellite scatterometer observations of the ocean surface wind speed and direction improve the depiction of storms at sea. Over the ocean, scatterometer surface winds are deduced from multiple measurements of reflected radar power made from several directions. In the nominal situation, the scattering mechanism is Bragg scattering from centimeter–scale waves, which are in equilibrium with the local wind. These data are especially valuable where observations are otherwise sparse—mostly in the Southern Hemisphere extratropics and Tropics, but also on occasion in the North Atlantic and North Pacific. The history of scatterometer winds research and its application to weather analysis and forecasting is reviewed here. Two types of data impact studies have been conducted to evaluate the effect of satellite data, including satellite scatterometer data, for NWP. These are simulation experiments (or observing system simulation experiments or OSSEs) designed primarily to assess the potential impact of plann...

Diagnostic Evaluation of Vertical Motion Forcing Mechanisms by Using Q-Vector Partitioning

Abstract Q-vector partitioning has proven to be a useful tool for the understanding of the frictionless, adiabatic processes responsible for the generation of synoptic-scale vertical motion in the extratropical atmosphere. Partitioning of Q into components parallel and normal to the isotherms on an isobaric surface is standard practice in studies dealing with vertical motion and frontogenesis. This paper is concerned with vertical motion only and examines the consequences of projecting Q onto isohypses, instead of isotherms, on an isobaric surface. Specifically, the Q vector is partitioned in the natural coordinate system that follows the geostrophic wind. The novelty with this partitioning is that it naturally leads to the evaluation of different vertical motion forcing mechanisms, among which are those related to flow curvature and to confluence or diffluence. This evaluation is illustrated by applying the new Q-vector partition to a gridded analysis of a real weather situation. An important conclusion ...

New Multiplatform Ocean Surface Wind Product Available

A new cross-calibrated, multiplatform (CCMP) ocean surface wind product with wide-ranging research applications in meteorology and oceanography became available at the Physical Oceanography Distributed Active Archive Center (PO.DACC) in May 2009. Data sets at three different levels of processing may be downloaded from http://podaac.jpl.nasa.gov/DATA_CATALOG/ccmpinfo.html. The principal data set, denoted as level 3.0, has global ocean coverage (except for the Arctic Ocean) with 25-kilometer resolution every 6 hours for more than 20 years, beginning in July 1987. Applying an enhanced variational analysis method (VAM) to multiple input data sources creates the level 3.0 data set. The VAM performs quality control and optimally combines wind observations from several individual satellite microwave radiometer and scatterometer sensors along with available conventional ship and buoy wind observations and European Centre for Medium-Range Weather Forecasts (ECMWF) analyses.

Diagnostic Evaluation of Numerical Model Simulations Using the Tendency Equation

Abstract A procedure is proposed to expand the diagnostic capabilities of the pressure tendency equation of a primitive equation NWP model by computing the pressure tendency in physical coordinates. The advantage of isolating the density advection as a diagnostic tool to understand pressure changes is shown. By simple thermodynamic arguments it is demonstrated that in areas of synoptic-scale cyclonic development, the vertically integrated density advection is more than sufficient to explain the depletion of mass over a growing depression. Consequently, the joint contribution of the net divergence and vertical motion opposes the pressure fall. This is illustrated for a case of rapid cyclogenesis in southern South America.