Marvin Geller - Academia.edu (original) (raw)

Papers by Marvin Geller

Atmospheric Chemistry and Physics, 2018

17th Conference on Climate Variability and Change/15th Conference on Atmospheric and Oceanic Fluid Dynamics/13th Conference on Middle Atmosphere, Jun 15, 2005

A design study for a high resolution meteor radar system is carried out with the objective of mea... more A design study for a high resolution meteor radar system is carried out with the objective of measuring upper atmospheric winds and particularly studying short period atmospheric waves in the 80 to 120 km altitude region. The transmitter that is to be used emits a peak power of 4 Mw. The system is designed to measure the wind velocity and height of a meteor trail very accurately. This is achieved using a specially developed digital reduction procedure to determine wind velocity and range together with an interferometer for measuring both the azimuth and elevation angles of the region with a long baseline vernier measurement being used to refine the elevation angle measurement. The resultant accuracies are calculated to be + or - 0.9 m/s for the wind, + or - 230 m for the range and + or - 0.12 deg for the elevation angle, giving a height accuracy of + or - 375 m. The prospects for further development of this system are also discussed.

Journal of Geophysical Research: Atmospheres, 2019

In this study, we estimate atmospheric turbulence in the free atmosphere in terms of the Thorpe s... more In this study, we estimate atmospheric turbulence in the free atmosphere in terms of the Thorpe scale (LT) and eddy dissipation rate (ε) using U.S. high vertical‐resolution radiosonde data over 4 years (September 2012 to August 2016) at 68 operational stations. In addition, same calculations are conducted for 12 years (October 2005 to September 2017) at four stations among the 68 stations. These high vertical‐resolution radiosonde data have a vertical resolution of approximately 5 m and extend to an altitude of approximately 33 km, and thus, turbulence can be retrieved in the entire troposphere and lower stratosphere. There are thicker and stronger turbulent layers in the troposphere than in the stratosphere, with mean ε values of 1.84 × 10−4 and 1.37 × 10−4 m2/s3 in the troposphere and stratosphere, respectively. The vertical structure of ε exhibits strong seasonal variations, especially in the upper troposphere and lower stratosphere, with the largest ε values in summer and the sm...

An evaluation of the land surface schemes against observations is essential, especially in the co... more An evaluation of the land surface schemes against observations is essential, especially in the context of time scales. Since the soil moisture reservoir has a memory considerably longer than that of most of the atmospheric processes, a climatic anomaly may persist through processes dependent on soil moisture. Accurate prediction of soil moisture is consequently important for GCMs simulations. The soil transport processes can carry climatic signals both upward and downward. Observations have provided a description of the soil moisture profile variability phase shift, fluctuation damping and persistence increasing with soil depth occur. This variability as a function of soil depth is linked to the time scales of the atmosphere, to a small extend, the climate spectra. Whether or not climate models can reproduce this variability should be a good test of their land process representations in the treatment of soil hydrology. Evaporation and transpiration are the primary mechanisms through...

In recent years, data assimilation has become an indispensable tool for our understanding of the ... more In recent years, data assimilation has become an indispensable tool for our understanding of the global features of meteorological variables. However, assessments of transport characteristics using trajectory related methods as well as chemical transport models (CTMs) show that results derived from assimilated (or analyzed) winds exhibit significantly larger mixing and entrainment rates compared to results derived from GCM winds, which are closer to results derived from observations (e.g., Douglass et al., 2002; Schoeberl et al., 2002). This discrepancy presents a serious challenge to our ability to understand and model global trace gas transport and distribution. We use the GEOS-DAS to explore this issue by examining how the process of data assimilation alters the dynamics of the underlying GCM and how this leads to the excess of lower stratospheric mixing and transport in the subtropics. In particular, we show that significant model biases in tropical winds necessitate large analy...

Journal of Atmospheric and Terrestrial Physics, 1971

... presented improved ion production rates based on new laboratory data including new 0 1,) phot... more ... presented improved ion production rates based on new laboratory data including new 0 1,) photoionization crosssections, and more * MEIBA'S measurements were made on winter days when the electron density was similar to that on an anomalous day. ...

Geophysical Research Letters, 1995

We present an example of observations within a single air mass of C10, C1ONO2, and HC1 from the i... more We present an example of observations within a single air mass of C10, C1ONO2, and HC1 from the instruments on the UARS spacecraft. A three-dimensional chemistry-transport calculation for HC1 is used to show that this air mass has been transported through regions cold enough for polar stratospheric cloud formation and chlorine activation through heterogeneous chemical reactions. These data, together with modeling of HC1 with and without heterogeneous loss as a qualitative measure of polar processing, indicate directly the transformation of the reservoirs HC1 and C1ONO2 to reactive chlorine species. 1. Introduction The discovery of the Antarctic ozone hole by Farman et al. (1985) has motivated extensive theoretical work, ground-based observations, and aircraft observations to better understand processes occurring in the Antarctic and Arctic that influence ozone loss. These impressive efforts have resulted in a generally accepted paradigm for polar processing of air on polar stratospheric clouds (PSCs) and the subsequent chemical reactions that deplete ozone. This paradigm begins with lower stratospheric temperatures becoming very cold in polar regions in early winter, resulting in the formation of an intense westerly polar vortex. When the temperatures become low enough, PSCs form, and reaction (1) takes place C1ONO2 + HC1-) HNO3 + C12 (1) Thus, we expect to see cold temperatures associated with enhanced PSC amounts (see-Hanson and Mauersberger, 1988), and this should lead to decreases in the atmospheric inactive chlorine species HCI and CIONO2. We also expect to see increases in active chlorine in the form of C10 + 2C120 2 + C1. Aircraft measurements have indicated that reaction (1) is occurring in the Antarctic and Arctic winters. Anderson et al. (1989) have measured the increases in CIO in the Antarctic and have shown that these CIO enhancements are highly correlated with 0 3 losses. Brune et al. (1990) have shown similar increases in CIO occurring in the Arctic. Webster et al. (1993) have shown

35th COSPAR Scientific Assembly, 2004

Effect of Geomagnetic disturbances on Mesosphere, etc. Solar Influence on Climate (Theme 1) Space... more Effect of Geomagnetic disturbances on Mesosphere, etc. Solar Influence on Climate (Theme 1) Space Weather: Science and Applications (Theme 2) Space Climatology (Theme 4) Atmospheric Coupling Processes (Theme 3

AGU Fall Meeting Abstracts, Dec 1, 2012

Six and one-half years of ozone data and temperature data are used to extend Geller et al.'s ... more Six and one-half years of ozone data and temperature data are used to extend Geller et al.'s (1988) study comparing the transport of ozone to high latitudes in the Northern and Southern Hemispheres. In this earlier study, it was pointed out that the poleward transport of ozone varies annually in the Northern Hemisphere but has a marked semiannual behavior in the Southern Hemisphere. This earlier study covered the period from December 1978 to November 1982. Two and one-half additional years have now been analyzed so that the analysis now extends to July 1986. With this extended data set, the maximum rate of increase in total ozone is seen to occur in January in the Northern Hemisphere for all of the years investigated. In the Southern Hemisphere, the maximum rate of increase is seen in September for almost all of the years with a secondary maximum in the rate of increase in total ozone often being seen during March-April period. The nature of the seasonal variation in total ozone...

ERA-40 data are analyzed to demonstrate that wave forcing at lower latitudes plays a crucial role... more ERA-40 data are analyzed to demonstrate that wave forcing at lower latitudes plays a crucial role in driving the tropical upwelling portion of the Brewer-Dobson circulation. It is shown that subtropical wave forcing is correlated with tropical upwelling on both intraseasonal and interannual time scales when transient waves are taken into account, and that tropical wave forcing exerts its influence on tropical upwelling via its body force on the zonal mean flow.

Atmospheric Measurement Techniques Discussions, 2017

We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS)... more We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is nine times better than that of the operational retrieval. HIRDLS provides 2D spectral formation of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short horizontal wavelength gravity waves and HIRDLS as a limb sounder is more sensitive to short vertical wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations...