Wind estimates from cloud motions: Preliminary results from phases 1, 2, and 3 of an in situ aircraft verification experiment

Low level aircraft equipped with Inertial Navigation Systems (INS) were used to define the vertical extent and horizontal motion of a cloud and to measure the ambient wind field. A high level aircraft, also equipped with an INS, took photographs to describe the horizontal extent of the cloud field and to measure cloud motion. The aerial photographs were also used to make a positive identification in a satellite picture of the cloud observed by the low level aircraft. The experiment was conducted over the tropical oceans in the vicinity of Florida, Puerto Rico, Panama and in the Western Gulf of Mexico. Results for tropical cumulus clouds indicate excellent agreement between the cloud motion and the wind at the cloud base. The magnitude of the vector difference between the cloud motion and the cloud base wind is less than 1.3 m/sec for 67% of the cases with track lengths of 1 hour or longer. The cirrus cloud motions agreed best with the mean wind in the cloud layer with a vector difference of about 1.6 m/sec

Goddard Laboratory for Atmospheric Science, collected reprints 1978-1979, volume 1

A ready reference is presented to 61 papers by members of the Laboratory published between January 1, 1978 and December 31, 1979. To avoid unnecessary duplication, only abstracts or introductions of NASA reports and conference proceedings are included with reprints of articles from various journals

Goddard Laboratory for Atmospheric Sciences, collected reprints 1978 - 1979, volume 2

Information about the Earth hydrosphere, obtained in the field and from aircraft and satellite imagery is reported. Particular emphasis is given to the use of microwave sensors in the study of soil moisture, sea ice, snow cover and atmospheric parameters associated with watersheds

Evaluation of the synoptic and mesoscale predictive capabilities of a mesoscale atmospheric simulation system

The overall performance characteristics of a limited area, hydrostatic, fine (52 km) mesh, primitive equation, numerical weather prediction model are determined in anticipation of satellite data assimilations with the model. The synoptic and mesoscale predictive capabilities of version 2.0 of this model, the Mesoscale Atmospheric Simulation System (MASS 2.0), were evaluated. The two part study is based on a sample of approximately thirty 12h and 24h forecasts of atmospheric flow patterns during spring and early summer. The synoptic scale evaluation results benchmark the performance of MASS 2.0 against that of an operational, synoptic scale weather prediction model, the Limited area Fine Mesh (LFM). The large sample allows for the calculation of statistically significant measures of forecast accuracy and the determination of systematic model errors. The synoptic scale benchmark is required before unsmoothed mesoscale forecast fields can be seriously considered

Star Formation in Sculptor Group Dwarf Irregular Galaxies and the Nature of "Transition" Galaxies

We present new H-alpha narrow band imaging of the HII regions in eight Sculptor Group dwarf irregular (dI) galaxies. Comparing the Sculptor Group dIs to the Local Group dIs, we find that the Sculptor Group dIs have, on average, lower values of SFR when normalized to either galaxy luminosity or gas mass (although there is considerable overlap between the two samples). The properties of ``transition'' (dSph/dIrr) galaxies in Sculptor and the Local Group are also compared and found to be similar. The transition galaxies are typically among the lowest luminosities of the gas rich dwarf galaxies. Relative to the dwarf irregular galaxies, the transition galaxies are found preferentially nearer to spiral galaxies, and are found nearer to the center of the mass distribution in the local cloud. While most of these systems are consistent with normal dI galaxies which currently exhibit temporarily interrupted star formation, the observed density-morphology relationship (which is weaker than that observed for the dwarf spheroidal galaxies) indicates that environmental processes such as ``tidal stirring'' may play a role in causing their lower SFRs.Comment: 35 pages, 10 figures, accepted for Feb 2003 AJ, companion to astro-ph/021117

The Interaction between the ISM and Star Formation in the Dwarf Starburst Galaxy NGC 4214

We present the first interferometric study of the molecular gas in the metal-poor dwarf starburst galaxy NGC 4214. Our map of the 12CO(1-0) emission, obtained at the OVRO millimeter array, reveals an unexpected structural wealth. We detected three regions of molecular emission in the north-west (NW), south-east (SE) and centre of NGC 4214 which are in very different and distinct evolutionary stages (total molecular mass: 5.1 x 10^6 M_sun). These differences are apparent most dramatically when the CO morphologies are compared to optical ground based and HST imaging: massive star formation has not started yet in the NW region; the well-known starburst in the centre is the most evolved and star formation in the SE complex started more recently. We derive a star formation efficiency of 8% for the SE complex. Using high--resolution VLA observations of neutral hydrogen HI and our CO data we generated a total gas column density map for NGC 4214 (HI + H_2). No clear correlation is seen between the peaks of HI, CO and the sites of ongoing star formation. This emphasizes the irregular nature of dwarf galaxies. The HI and CO velocities agree well, so do the H-alpha velocities. In total, we cataloged 14 molecular clumps in NGC 4214. Our results from a virial mass analysis are compatible with a Galactic CO-to-H_2 conversion factor for NGC 4214 (lower than what is usually found in metal-poor dwarf galaxies).Comment: accepted for publication in the AJ (February 2001), full ps file at: ftp://ftp.astro.caltech.edu/users/fw/ngc4214/walter_prep.p

A Spitzer/IRAC Census of the Asymptotic Giant Branch Populations in Local Group Dwarfs. I. WLM

We present Spitzer/IRAC observations at 3.6 and 4.5 microns along with optical data from the Local Group Galaxies Survey to investigate the evolved stellar population of the Local Group dwarf irregular galaxy WLM. These observations provide a nearly complete census of the asymptotic giant branch (AGB) stars. We find 39% of the infrared-detected AGB stars are not detected in the optical data, even though our 50% completeness limit is three magnitudes fainter than the red giant branch tip. An additional 4% of the infrared-detected AGBs are misidentified in the optical, presumably due to reddening by circumstellar dust. We also compare our results with those of a narrow-band optical carbon star survey of WLM, and find the latter study sensitive to only 18% of the total AGB population. We detect objects with infrared fluxes consistent with them being mass-losing AGB stars, and derive a present day total mass-loss rate from the AGB stars of 0.7-2.4 x 10^(-3) solar masses per year. The distribution of mass-loss rates and bolometric luminosities of AGBs and red supergiants are very similar to those in the LMC and SMC and the empirical maximum mass-loss rate observed in the LMC and SMC is in excellent agreement with our WLM data.Comment: Accepted by ApJ, 34 pages, 13 figures, version with high-resolution figures available at: http://webusers.astro.umn.edu/~djackson