Comparison of TEC prediction methods in mid-latitudes with GIM maps

There are many long-term and short-term prediction methods of Total Electron Content(TEC) that need to be tested for each specific region. Recently, much attention has been paid to testing TEC models in high-, low-latitude and equatorial regions. This paper compares the TEC prediction methods in the midlatitude zone according to the data of the Juliusruh, Rostov, Manzhouli stations in 2008 and 2015. For a long-term prediction, the IRI-Plas and Ne Quick models are compared with the Global Ionospheric Maps(GIM) presented by the Jet Propulsion Laboratory(JPL) and the Technical University of Catalonia(UPC).For a short-term prediction, the Standard Persistence Model(SPM) method, a 27 day median model, and the proposed short-term prediction method are compared for one day ahead. It is shown that for all stations the IRI-Plas model provides better compliance with GIM maps than the Ne Quick model irrespective of a solar activity level. An average absolute error lays in the range of 3 e3.5 TECU, relative root square mean(RMS) error in the range of 22 e27% in 2015 and 1.7 e2 TECU, 20 e25% in 2008. For the Ne Quick model, these estimates were 6.7 e8.2 TECU and 42 e45% in 2015 and 2.2 e3.6 TECU, 30 e37% in2008. For the short-term forecast, the best results were obtained by the SPM method with an average absolute error in the range of 1.95 e2.15 TECU in 2015 and 0.59 e0.98 TECU in 2008, a relative RMS error in the range of 17 e21% in 2015, 11.5 e15% in 2008. For the proposed short-term prediction method, these errors were 2.04 e2.2 TECU and 12 e14% in 2015 and 0.7 e1.0 TECU, 7 e11% in 2008. Using medians, the errors were 3.1 e3.4 TECU and 17 e21% in 2015 and 1.0 e1.3 TECU, 10 e15% in 2008. The dependence of results on the Dst-index was obtained.

Distribution of the Permian Monodiexodina in Karakorum and Kunlun and its Geological Significance

The Permian fusulinoidean genus Monodiexodina is widely distributed in east Tethys. The genus might be an important indicator for the northern margin of Gondwana in northwestern China, but this is disputed. Monodiexodina-bearing areas can be restored as in either northern or southern middle latitudes with a symmetrical distribution between a high latitudinal, cool/cold water climatic realm and a paleotropical, warm water realm. Permian strata bearing Monodiexodina in Karakorum, Muztag Pear, and Buka Daban Pear of the east Kunlun Mountains can be correlated with each other. Faunal analyses and the stratigraphical position of Monodiexodina-bearing strata indicate that both Karakorum, east Kunlun, and the Pamirs were formed in a cool temperate sea area of the northern hemisphere in middle latitudes during the Permian, rather than at the Gondwana margin.

DEVELOPING AND NON-DEVELOPING TROPICAL CYCLONES AS REVEALED BY HIGH DENSITY CLOUD MOTION WINDS

An algorithm for computation of cloud motion winds has been developed at the National Satellite Meteorological Center in China. Since 1997, it has been applied to calculate the cloud motion winds for a 1.25 lat. ×1.25 long. mesh over the northwest Pacific region with the satellite data from GMS-5. The development of the tropical cyclones is studied. It shows that the tropical cyclone is usually intrigued by the westerly jet streams at the upper levels of the troposphere, which may be caused by mid-latitude troughs well extending into the tropics. During the prime season of summer, the westerly flowing equatorward of the TUTT may also be a cause for the generation of typhoons.

INFLUENCE OF THE BASIC FLOW IN THE TROPICS ON THE STATIONARY PLANETARY WAVES AT MIDDLE AND HIGH LATITUDES DURING THE NORTHERN HEMISPHERE WINTER

The relationship between the quasi-stationary planetary waves forced by topography and heat source during the Northern Hemisphere winter is investigated by means of a quasi-geostrophic,34-level,spherical coordinate model with the Rayleigh friction,the Newtonian cooling and the horizontal eddy thermal diffu- sion. The calculated results show that when the basic flow is the westerly in the tropical stratosphere,the amplitude of quasi-stationary planetary wave for zonal wavenumber 2 at middle and high latitudes is larger during the Northern Hemispheric winter;while when the basic flow is the easterly,it is smaller.This is in agreement with the observed results. The calculated results also show that influence of the basic flow in the tropical troposphere on the quasi- stationary planetary waves is larger than that of the basic flow in the tropical stratosphere on the quasi- stationary planetary waves.

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC

There is a close relationship between variation of middle latitude synoptic system over the Tibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discuss the mechanism of it through the numerical simulation and dynamic diagnosis. 25-year statistical results during the period from 1970 to 1995 indicate that the relationship between middle latitude circulation over the Plateau and the track of typhoon over the Northwest Pacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it is favourable to typhoon's westward movement:on the contrary,large scale anticyclone over the Plateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flow patterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on 500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon south to high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bring about the longwave trough developing along the east coast of Asia,it'will usually cause typhoon recurring in front of the developed trough. In addition,the results of dynamic diagnosis show the physical mechanism on impact of synoptic system over the Plateau on the downstream synoptic system,that is,the transport of disturbance kinetic energy over the upstream Plateau makes the downstream trough developed. And then it affects the steering flow of typhoon.Because of existence of the high ridge over the Plateau.the energy transport channel moves to north.On the contrary,the trough exists over the Plateau,the energy transport channel moves to south.The southerly in front of trough over the Plateau and the southerly in the east part of typhoon transport low potential vorticity of low latitude into subtropical high.That is beneficial to development of subtropical high and affects typhoon's movement.These results fully reflect the impact of interaction between mid-latitude and low latitude on synoptic system.

Atmospheric Structure Observed over the Antarctic Plateau and Its Response to a Prominent Blocking High Event

Studies on the atmospheric structure over the Antarctic Plateau are important for better understanding the weather and climate systems of polar regions.In the summer of 2017,an observational experiment was conducted at Dome-A,the highest station in Antarctica,with a total of 32 profiles obtained from global positioning system(GPS)radiosondes.Based on observational data,the atmospheric temperature,humidity,and wind structures and their variations are investigated,and compared with those from four other stations inside the Antarctic circle.Distinguished thermal and dynamic structures were revealed over Dome-A,characterized by the lowest temperature,the highest tropopause,the largest lapse rate,and the most frequent temperature and humidity inversion.During the experiment,a prominent blocking event was identified,with great influence on the atmospheric structure over Dome-A.The blocking high produced a strong anticyclone that brought warm and moist air to the hinterland of the Antarctic Plateau,causing a much warmer,wetter,and windier troposphere over the Dome-A station.Meanwhile,a polar air mass was forced out of the Antarctic,formed a cold surge extending as far as southern New Zealand and affected the weather there.Our results proved that there would be a direct interaction between the atmosphere over the hinterland of the Antarctic Plateau and mid latitudes with the action of a blocking high.Further studies are needed to explore the interaction between the atmospheric systems over the Antarctic and mid latitudes under intense synoptic disturbance,with longterm data and numerical modeling.