摘要:

The limb infrared monitor of the stratosphere, stratospheric and mesospheric sounder, and solar backscatter ultraviolet satellite measurements of stratospheric T, O3, NO2, HNO3, H2O, CH4, and solar flux are used in conjunction with a zero‐dimensional, stratospheric, photochemical model to infer distributions of other constituents. For periods in October and December 1978 and in March and May 1979, latitude‐altitude distributions of O(3P), O(1D), OH, HO2, H2O2, NO, NO3, N2O5, HNO4, HCℓ, Cℓ, CℓO, CℓNO3, HOCℓ, total odd nitrogen, and total odd hydrogen are derived and presented. Results are presented for altitudes from 20.5 km to 53.5 km and for latitudes from 60°S to 80°N with some variation depending upon season. The techniques used are described. They require the specification of the distribution of the total odd chlorine due to the absence of satellite measurements of chlorine species. Two‐dimensional model results for odd chlorine, scaled to provide the required level of total odd chlorine for the 1978–1979 time period, were used. Sensitivity of results to input values of CH4(for which some extrapolation was required) and odd chlorine is presented and discussed. Uncertainties in the inferred species due to uncertain chemical rates, cross sections, and measurement errors are presented. Results provide a useful climatology of these infrequently measured species for the four time periods. Of particular interest are maximum odd nitrogen (≡NO + NO2+ NO3+ HNO3+ HNO4+ CℓNO3+ 2 × N2O5) levels which range between 24 and 27 ppbv, significantly higher than predicted by

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01167

年代:1986

数据来源: WILEY

摘要:

Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) observations are used to study the evolution of potential vorticity in the stratosphere, January–February 1979. Daily analysis of this quantity at 850° and 1200°K provides circumstantial evidence of planetary wave “breaking” by which air parcels undergo rapid and irreversible separation from the circumpolar vortex during stratospheric warmings. Complementing this effect is the advection of subtropical, low‐vorticity air into the polar region. Temporal evolution of the size, shape, and orientation of the main circumpolar vortex is revealed very clearly by the potential vorticity field. All three factors are important, although some have been emphasized more strongly in previous literature. The size of the vortex determines the range of latitudes over which planetary Rossby waves are able to propagate vertically. Diminution of vortex area during the observed warmings is believed to precondition the flow, focusing subsequent Rossby wave activity into the polar cap, as in the major warming of late February 1979. The shape of the vortex undergoes both reversible and irreversible deformation. Examples of irreversible deformation are seen in the advective formation of extended high‐vorticity tongues over subtropical latitudes in connection with the warmings of late January, early February, and late February 1979. Two of these were recently discussed by McIntyre and Palmer. Reversible deformation is observed in the sudden cooling and concurrent wave 1, wave 2 vacillation, after the January warming. The orientation of the vortex can also be important, as in the period of rotation leading up to the major wave 2 warming of late February 1979. We suggest that the orientation of the vortex be included as part of the preconditioning process, in accord with numerical results of Butchart et al. We briefly consider the vertical structure of potential vorticity and ozone on two disturbed days in late January 1979. Meridional cross sections of potential vorticity in the middle stratosphere resemble ozone cross sections shown in the work of Leovy et al. and exhibit good vertical coherence extending into the lower mesosphere, where ozone (unlike potential vorticity) no longer serves as a tracer of

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01199

年代:1986

数据来源: WILEY

摘要:

A nearly inertial evolution of the relative velocities measured by differential sounding (Barat, 1982a) has been observed along a balloon flight in the 26–30 km altitude range. The vertical structure of the flow appears to be a stack of layers a few hundred meters wide undergoing independent, nearly inertial oscillations added to the mean flow, the transitions between adjacent layers being characterized by abrupt rotations of the horizontal wind. We show that the stability of such a structure, despite the very high wind shears encountered within transitions, is consistent with the very weak turbulent viscosity coefficient independently estimated. As a tentative interpretation of our observations we suggest that they are related to the dissipation of an internal gravity wave near a critical leve

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01209

年代:1986

数据来源: WILEY

摘要:

Atmospheric gravity waves are subject to horizontal ducting in a stably stratified atmosphere that contains levels of wind maximum or minimum, quite apart from any superimposed consequences of vertical variation of stability and quite apart from the existence or otherwise of critical levels. The process, “Doppler ducting”, is examined here for two prototype cases (an isolated wind maximum and a wind minimum at ground level) and for two more realistic model cases (a strong tropospheric jet and a nocturnal boundary layer jet). The wave structure, modal behavior, and dispersion curves of all four are very similar. It is argued that Doppler ducting is available to a part of the gravity wave spectrum in all real circumstances and that it should be considered as a possible candidate whenever observations indicate that some ducting process is operative. One particular wave event is discussed in some detail, and it is shown that Doppler ducting in its simplest form provides a plausible alternative to a more complicated ducting process (which involved critical levels and energy leakage) previously inferred. Doppler ducting is available equally to gravity waves in the oceans when background currents vary with de

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01219

年代:1986

数据来源: WILEY

摘要:

Instrumented aircraft and radar were used to investigate the microphysical, electrical, and dynamic evolution of the life cycle of a small thunderstorm which occurred in southeastern Montana. The observations commenced as precipitation development was just beginning, continued through the active stage of growth as the cloud produced graupel up to 8 to 9 mm diameter and reflectivities aloft of 45 dBZ, through the dissipation stage when only an anvil with a trail of light precipitation remained. The largest particles and the primary development of precipitation were found to occur in the fringes of the updraft. The electric fields inside the cloud did not exceed 100 V m−1until 5 mm graupel, ice particle concentrations of 10 L−1, and reflectivities of 35 dBZ were already present, but then rapidly electrified to produce a single intracloud discharge 8 min later, near the peak of microphysical development. Early in the electrical development of the cloud when observed electric fields were only 200 V m−1, negative charge accumulation was observed near the 7 km (−20°C) level and was associated with the high reflectivity region. In the early stages of precipitation fallout, particle charge measurements near 4.5 km showed primarily negatively charged particles which appeared to be associated with precipitation falling from the cloud. Less than 5 to 10% of the observed particles larger than 100 μm were carrying charges larger than 5 pC, the detection limit of the instrument. These observations are discussed from the point of view of charge generation in thunderstorms, particularly, charge transfer between colliding ice

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01231

年代:1986

数据来源: WILEY

摘要:

A 300‐MHz interferometric imaging system has been used for the characterization of the VHF‐UHF electromagnetic radiation from lightning flashes. Results are presented, with emphasis on typical phenomenology, in particular through correlations with the electrical activity description from an E field sensor network. At the microsecond time scale the VHF‐UHF radiation appears impulsive, either as low rate pulsed emissions or as bursts of pulses. The low‐rate emissions (below 20 pulses/ms) are usually present during important intracloud charge transfers and correspond to spread out sources over distances of the order of 1 km. The bursts last from several hundred microseconds to a few milliseconds, and they are associated with highly organized propagations of sources in the 107‐m/s velocity range extending over distances of several kilometers. They appear in all phases of the lightning flash and are not associated with large charge transfers. Their spatial evolution and chronology with respect to the electrical phenomenology, in particular during precursor phenomena, indicate a decorrelation between electromagnetic phenomenology and the typical electrical phen

ISSN:0148-0227    

DOI:10.1029/JD091iD01p01248

年代:1986

数据来源: WILEY