Cardiac output and regional blood flow in conscious rats exposed to acute hypoxia

Cardiac output and regional blood flow in conscious rats exposed to acute hypoxi

The influence of the spectral truncation on the simulation of waves in the tropical stratosphere

Convectively triggered waves are the main driver of the tropical stratospheric circulation. In atmospheric models, the model’s resolution limits the length of the simulated wave spectrum. In this study, the authorscompare the tropical tropospheric wave sources, their projection on the wave field in the lower stratosphere, and the circumstances of their upward propagation in the atmospheric model ECHAM6 with three spectral truncations of T63, T127, and T255. The model internally generates the quasi biennial oscillation (QBO),which dominates the variability in the tropical stratosphere. This analysis focuses on two opposite phases of the QBO to account for the influence of the background wind field on the wave filtering. It is shown that, compared to the high-resolution model versions, the T63 version has less convective variability and less wave momentum in the lower stratosphere at wavenumbers larger than 20, well below the version’s truncation limit.In the low-resolution version, the upward propagation of the waves is further hindered by the highly active (relative to the high-resolution versions) horizontal diffusion scheme. However, even in the T255version of ECHAM6, the convective variability is too small compared to TRMM observations at periods shorter than 2 days and wavelengths shorter than 1000 km. Hence, to model a realistic tropical waveactivity, the convective parameterization of the model has to improve to increase the day-to-day precipitation variability

Modification of Jupiter's Stratosphere Three Weeks After the 2009 Impact

Infrared spectroscopy sensitive to thermal emission from Jupiter's stratosphere reveals effects persisting 3 1/2 weeks after the impact of a body in late July 2009. Measurements obtained at 11.7 microns on 2009 August 11 UT at the impact latitude of 56degS (planetocentric), using the Goddard Heterodyne Instrument for Planetary Winds and Composition (HIPWAC) mounted on the NASA Infrared Telescope facility, reveal an interval of reduced thermal continuum emission that extends approx.60deg-80deg towards planetary East of the impact site, estimated to be at 305deg longitude (System III). Retrieved stratospheric ethane mole fraction in the near vicinity of the impact site is enhanced by up to approx.60% relative to quiescent regions at this latitude. Thermal continuum emission at the impact site, and somewhat west of it, is significantly enhanced in the same spectra that retrieve enhanced ethane mole fraction. Assuming that the enhanced continuum brightness near the impact site results from thermalized aerosol debris, then continuum emission by a haze layer can be approximated by an opaque surface inserted at the 45-60 mbar pressure level in the stratosphere in an unperturbed thermal profile, setting a lower limit on the altitude of the top of the ejecta cloud at this time. The reduced continuum brightness east of the impact site can be modeled by an opaque surface near the cold tropopause, consistent with a lower altitude of ejecta/impactor-formed opacity or significantly lesser column density of opaque haze material. The physical extent of the observed region of reduced continuum implies a minimum average velocity of 21 m/s transporting material prograde (East) from the impact. Spectra acquired further East, with quiescent characteristics, imply an average zonal velocity of less than 63 m/s

Spatial and temporal variations of aerosols around Beijing in summer 2006: Model evaluation and source apportionment

Regional aerosol model calculations were made using the Weather Research and Forecasting (WRF)-Community Multiscale Air Quality (CMAQ) and WRF-chem models to study spatial and temporal variations of aerosols around Beijing, China, in the summer of 2006, when the Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing) intensive campaign was conducted. Model calculations captured temporal variations of primary (such as elemental carbon. (EC)) and secondary (such as sulfate) aerosols observed in and around Beijing. The spatial distributions of aerosol optical depth observed by the MODTS satellite sensors were also reproduced over northeast China. Model calculations showed distinct differences in spatial distributions between primary and secondary aerosols in association with synoptic-scale meteorology. Secondary aerosols increased in air around Beijing on a scale of about 1000 × 1000 km2 under an anticyclonic pressure system. This air mass was transported northward from the high anthropogenic emission area extending south of Beijing with continuous photochemical production. Subsequent cold front passage brought clean air from the north, and polluted air around Beijing was swept to the south of Beijing. This cycle was repeated about once a week and was found to be responsible for observed enhancements/reductions of aerosols at the intensive measurement sites. In contrast to secondary aerosols, the spatial distributions of primary aerosols (EC) reflected those of emissions, resulting in only slight variability despite the changes in synopticscale meteorology. In accordance with these results, source apportionment simulations revealed that primary aerosols around Beijing were controlled by emissions within 100 km around Beijing within the preceding 24 h, while emissions as far as 500 km and within the preceding 3 days were found to affect secondary aerosols. Copyright 2009 by the American Geophysical Union

An Extended View of Ozone and Chemistry in the Atmosphere of Mars

We present an ongoing effort to characterize chemistry in Mars' atmosphere in multiple seasons on timescales longer than spaceflight missions through coordinated efforts by GSFC's HIPWAC spectrometer and Mars Express SPICAM, archival measurements, and tests/application of photochemical models. The trace species ozone (03) is an effective probe of Mars' atmospheric chemistry because it is destroyed by odd-hydrogen species (HOx, from water vapor photolysis). Observed ozone is a critical test for specific predictions by 3-D photochemical models (spatial, diurnal, seasonal). Coordinated measurements by HIPWAC and SPICAM quantitatively linked mission data to the 23-year GSFC ozone data record and also revealed unanticipated inter-decadal variability of same-season ozone abundances, a possible indicator of changing cloud activity (heterogeneous sink for HOx). A detailed study of long-term conditions is critical to characterizing the predictability of Mars' seasonal chemical behavior, particularly in light of the implications of and the lack of explanation for reported methane behavior

Probing the Distribution of Ozone on Mars

We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by photochemistry-coupled general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry in Mars' atmosphere, serving as an observable with which to test predictions of photochemical models. Infrared heterodyne measurements of ozone absorption features on Mars have been obtained at various Martian seasons from 1988 until present at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i [I]. The NASAiGoddard Space Flight Center spectrometers used were the Infrared Heterodyne Spectrometer (IRHS) [2, 3] and, since 2003, the Heterodyne Instrument for Planetary Wind and Composition (HIPWAC) [4]. A description the infrared heterodyne technique applied to ground-base observations of Martian ozone can be found in [I]. The most recent measurements on February 21-24 2008 UT at Ls=35deg were made by HIPWAC on or near the Mars Express orbital path with the goal of acquiring spectra that can be directly compared to nadir observations by SPICAM

Ground Based Observation of Isotopic Oxygen in the Martian Atmosphere Using Infrared Heterodyne Spectroscopy

Infrared heterodyne spectra of isotopic CO2 in the Martian atmosphere were obtained using the Goddard Heterodyne Instrument for Planetary Wind and Composition, HIPWAC, which was interfaced with the 3-meter telescope at the NASA Infrared Telescope Facility- Spectra were colle cted at a resolution of lambda/delta lambda=10(exp 7). Absorption fea tures of the CO2 isotopologues have been identified from which isotop ic ratios of oxygen have been determined. The isotopic ratios O-17/O -16 and O-18/O-16 in the Martian atmosphere can be related to Martian atmospheric evolution and can be compared to isotopic ratios of oxyg en in the Earth's atmosphere. Isotopic carbon and oxygen are importa nt constraints on any theory for the erosion of the Martian primordia l atmosphere and the interaction between the atmosphere and surface o r subsurface chemical reservoirs. This investigation explored the pr esent abundance of the stable isotopes of oxygen in Mars' atmospheric carbon dioxide by measuring rovibrational line absorption in isotop ic species of CO2 using groundbased infrared heterodyne spectroscopy in the vicinity of the 9.6 micron and 10.6 micron CO2 lasing bands. T he target transitions during this observation were O-18 C-12 O-16 as well as O-178 C-12 O-16 and O-16 C-113 O-16 at higher resolving power of lambda/delta lambda=10(exp 7) and with high signal-to-noise ratio (longer integration time) in order to fully characterize the absorpt ion line profiles. The fully-resolved lineshape of both the strong n ormal-isotope and the weak isotopic CO2 lines were measured simultane ously in a single spectrum