Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

Retrograding Wintertime Low-Frequency Disturbances over the North Pacific Ocean

Abstract: Retrograding (westward-moving) features over the middle and high latitudes of the Northern Hemisphere during winter are examined in observations and data from a GCM simulation, using complex principal component analysis. The first eigenvector of the low-frequency middle troposphere geopotential height over the North Pacific has a zonal scale of 120–160 deg longitude and a dipole-like meridional structure, with maximum amplitude over the Gulf of Alaska and the Bering Sea. These disturbances propagate westward and go through a life cycle of growth and decay over a period of about three weeks. The temporal evolution of the energy and its conversions during the life cycle of the simulated Pacific disturbances are composited, using the time-dependent coefficient of the principal component analysis as an index for their occurrence. The composite energy cycle indicates that the kinetic and available potential energy of these disturbances grow and decay together. Both baroclinic and barotropic conversion...

Global and seasonal distribution of gravity wave activity in Mars' lower atmosphere derived from MGS radio occultation data

Abstract: [1] Temperature profiles from Mars Global Surveyor (MGS) radio occultation measurements reveal vertical wave structures assumed to be atmospheric gravity waves in Mars' lower atmosphere. For each vertical temperature profile derived from a radio occultation measurement, wave energy density is calculated, and results are locally averaged to derive a global distribution of gravity wave activity. Global distributions are determined for all values of solar longitude and for solar longitudes corresponding to northern summer and winter to show seasonality and for vertical wavelengths less than 10 km to remove the contribution from thermal tides, which dominate in the Martian tropics at larger vertical wavelengths. The global energy density patterns show significant wave activity over the tropics and the mountainous Tharsis region averaged over all seasons and enhanced activity in northern summer compared to winter. For the most part, the observed data does not correlate well with the orographic forcing schemes used to model gravity waves in general circulation models for Mars, suggesting that wave sources other than orography play an important role on Mars.

Evidence for a Fundamental Period of the Sun and Its Relation to the 154 Day Complex of Periodicities

Abstract: We have analyzed the longitude distributions of major flares observed in the 1955-1991 interval, referring them to coordinate systems rotating about axes tilted with respect to the rotation axis of the solar envelope. We find that the longitude distribution exhibits the largest modulation in the coordinate system with the following parameters: rotation period, 25.50 days; tilt angle of the rotation axis, 40 deg; tilt direction, toward the position of the earth on December 4 in its orbit around the sun. We interpret this as being due to an obliquely rotating structure (or a wave pattern rotating about an oblique axis) which has two exciters. We identify the period of 25.50 days as the fundamental period of the hypothetical 'clock' proposed by Bai and Sturrock (1991). The periods of the subharmonics are 51.0, 76.5, 102.0, 127.5, and 153.0 days, in agreement with periodicities found from analysis of flare occurrence times.

Diurnal cycle of tropical precipitation in a general circulation model

Abstract: [1] Hourly averaged precipitation rates from an ensemble of the Community Climate Model version 3 (CCM3) simulations for the 44-month period from January 1998 through August 2001 are compared to observations from the Tropical Rainfall Measuring Mission (TRMM) satellite In order to have adequate sampling by the satellite, comparisons are made for 15° longitude × 10° latitude boxes and for larger geographical areas within the tropics The temporally and spatially averaged hourly precipitation rates from CCM3 and from TRMM are fit to the diurnal harmonic by the method of linear least squares regression, and the phases and the amplitudes of the diurnal cycles are compared The model's diurnal cycle is too strong over major land masses, particularly over South America (200% too large), and is too weak over many oceans, particularly the northwestern tropical Pacific (57% too small) The model-satellite phase differences tend to be more homogeneous The peak in the model's diurnal harmonic consistently precedes that of the observations nearly everywhere Phase differences are large over Australia, Papua New Guinea, and Saharan Africa, where CCM3 leads TRMM by 4 hours, 5 to 6 hours, and 9 to 11 hours, respectively The model's phase and amplitude biases likely have effects on its hydrologic cycle and its surface and atmospheric energy budgets Thus the causes for the model's biases need to be investigated