Hurricane and tropical storm statistics verify the modulation of eastern Pacific tropical systems by the Madden– Julian oscillation (MJO) as hypothesized by Maloney and Hartmann. Over twice as many named tropical systems (hurricanes and tropical storms) accompany equatorial 850-mb westerly anomalies than accompany equatorial easterly anomalies, and the systems that do exist are stronger. Hurric...

Intraseasonal fluctuations of the large scale divergent circulation of the tropical troposphere during the one year period December 1, 1978 November 30, 1979 are examined using analyses prepared by the European Centre for Medium Range Weather Forecasts (ECMWF). It is demonstrated through a number of empirical orthogonal function (EOF) analyses that highly coherent, equatorially symmetric fluctu...

During the years 1899-1967, in temperate latitudes of the Northern Hemisphere, there has been a significant quasi-periodic fluctuation (hereafter denoted as periodicity) of about 16 yr. in the even minus odd (even-odd) year difference in sea level zonal geostrophic wind for the months January through May. No such periodicity is evident for the months July through November. For the winter and sp...

MF radar wind measurements in the mesosphere and lower thermosphere over Poker Flat, Alaska (65.1 N, 147.5 W) are used to study the features of mean winds and solar tides. Continuous observation with the newly installed radar is in progress and in the present study we have analyzed a database of the first 27 months (October 1998–December 2000) of observation. The observed mean wind climatology ...

Idealized experiments with the Whole Atmosphere Community Climate Model (WACCM) are used to explore the mechanism(s) whereby the stratospheric quasi-biennial oscillation (QBO) modulates the Northern Hemisphere wintertime stratospheric polar vortex. Overall, the effect of the critical line emphasized in the Holton–Tan mechanism is less important than the effect of the mean meridional circulation...

Different factors influencing the changes in the zollally averaged wind are investigated. It is evident from recent investigations of errors in the zonally averaged winds in the rron-divergent, one-parameter model that the convergence of the meridional transport of zonal momentum concentrat,es too rnuch momentum in the middle latitudes and predicts too small amounts of rnonlenturn in t>he low a...

The climatology of atmospheric horizontal wind and its vertical gradient, i.e. wind-shear, is characterized as a function of climate region. For a better representation of the average atmospheric wind and shear and their variabilities, high-resolution radiosonde wind profiles up to about 30 km altitude are compared with collocated operational ECMWF-model ShortRange Forecast winds. Statistics of...

We present a short review of our current knowledge on Saturn’s stratospheric thermal structure and composition (hydrocarbons) based on recent Cassini/CIRS observations. Anomalies in the temperature field and in the meridional distribution of hydrocarbons hint at atmospheric dynamical phenomena at play. The two most notable features are an obseved asymmetry in the hydrocarbons distribution at hi...

Gravity waves (GWs) greatly influence the background state of the middle atmosphere by imposing their momentum on the mean flow upon breaking and by thus driving, e.g., the upper mesospheric summer zonal wind reversal. In this situation momentum is conserved by a balance between the vertical divergence of GW momentum flux (the so-called GW drag) and the Coriolis acceleration of the mean meridio...

Based on an empirical analysis of measurements with the High Resolution Doppler Imager (HRDI) on the UARS spacecraft in the upper mesosphere (95 km), persistent and regular intra-seasonal oscillations (ISO) with periods of about 2 to 4 months have recently been reported in the zonal-mean meridional winds. Similar oscillations have also been discussed independently in a modeling study, and they ...