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.

Three‐dimensional change in temperature sensitivity of northern vegetation phenology

Abstract: Understanding how the temperature sensitivity of phenology changes with three spatial dimensions (altitude, latitude, and longitude) is critical for the prediction of future phenological synchronization. Here we investigate the spatial pattern of temperature sensitivity of spring and autumn phenology with altitude, latitude, and longitude during 1982-2016 across mid- and high-latitude Northern Hemisphere (north of 30°N). We find distinct spatial patterns of temperature sensitivity of spring phenology (hereafter "spring ST ") among altitudinal, latitudinal, and longitudinal gradient. Spring ST decreased with altitude mostly over eastern Europe, whereas the opposite occurs in eastern North America and the north China plain. Spring ST decreased with latitude mainly in the boreal regions of North America, temperate Eurasia, and the arid/semi-arid regions of Central Asia. This distribution may be related to the increased temperature variance, decreased precipitation, and radiation with latitude. Compared to spring ST , the spatial pattern of temperature sensitivity of autumn phenology (hereafter "autumn ST ") is more heterogeneous, only showing a clear spatial pattern of autumn ST along the latitudinal gradient. Our results highlight the three-dimensional view to understand the phenological response to climate change and provide new metrics for evaluating phenological models. Accordingly, establishing a dense, high-quality three-dimensional observation system of phenology data is necessary for enhancing our ability to both predict phenological changes under changing climatic conditions and to facilitate sustainable management of ecosystems.

On the Role of the Tropics in the General Circulation of the Atmosphere

Abstract: Contrary to older descriptions, the air currents in the middle and upper troposphere over the low latitudes are not steady but highly variable. There are trains of well-developed waves or vortices. When these disturbances combine with troughs in the polar westerlies, the resulting extended troughs often reach from pole to equator. Poleward flow of heat must take place mainly along these troughs. Energy from low latitudes is injected into the temperate zone in narrow and variable areas only. A description of the tropical atmosphere in the layers below and above the bases of the cumuli leads to an attempt to explain the steadiness of the low-level wind field which contrasts with the high variability of the upper layers. Then the strength of the mean meridional circulation and the fields of divergence and convergence at the surface are calculated, followed by a summary of available information on the high-level circulation. The field of motion aloft varies greatly with longitude, so that inferences concerning the tropics as a whole can only be made from maps covering most longitudes. Such maps (300-mb charts) are available for a limited period down to latitude 10° N. They indicate that regions where the easterlies decrease upward alternate with regions of increasing easterlies. DOI: 10.1111/j.2153-3490.1950.tb00306.x

The Free Oscillations of Fluid on a Hemisphere Bounded by Meridians of Longitude

Abstract: A precise calculation is presented of the normal modes of oscillation of an ocean of uniform depth which is bounded by two meridians of longitude separated by an angle of 180°. The calculation takes full account of the horizontal divergence of the motion, and so is applicable to both barotropic and baroclinic modes of oscillation.At small values of the parameter (defined fully in § 1) the calculation yields both the familiar gravity waves and also the nondivergent planetary waves computed in an earlier paper (Longuet-Higgins 1966). At large, positive values of e , corresponding to baroclinic waves, new types of oscillation appear in which the flux of energy is concentrated near the equator, the circuit being completed by Kelvin waves along the meridianal boundaries. The calculated frequencies are compared with asymptotic expressions derived from a recent beta-plane analysis by D. W. Moore. Solutions are also found corresponding to negative values of e . These must be included in a complete calculation of the response of the ocean to external forces. At small values of e these solutions resemble the planetary waves. At large (negative) values of e they represent almost-inertial motions concentrated near the poles, having a phase-velocity towards the east and an amplitude modulated so as to vanish at the boundaries. The calculations are relevant to the real ocean in so far as they show the kinds of oscillation that might be expected in any ocean basin including any section of the equator (or including a pole). They also indicate the degree of accuracy to be expected in computing the frequencies of the normal modes by beta-plane methods.