Latitude and diurnal variations of air densities from 190 to 280 km as derived from the orbits of Discoverer satellites

1961 ◽  
Vol 263 (1313) ◽  
pp. 212-216 ◽  
Keyword(s):  
Density Profile ◽  
Polar Region ◽  
Local Heating ◽  
Scale Height ◽  
Diurnal Variations ◽  
Night Time ◽  
Air Density ◽  
Region Data ◽  
Time Density

Variations in air density between day and night in the region 190 to 280 km are found to be small (less than about 25%). The presence of a ‘wiggle’ in the curve of log (day-time density) against height indicates a possible region of local heating at about 220 km which disappears at night. The night-time density profile conforms with a constant scale height of 35(± 2) km. No definite variation of air density with latitude is evident apart from a possible increase of about 60%, which is indicated by rather limited polar-region data. For other latitudes and seasons a variation of less than about 20% is indicated.

Determination of upper-atmosphere air-density profile from satellite observations

1959 ◽  
Vol 252 (1268) ◽  
pp. 28-34 ◽  
Keyword(s):  
Density Profile ◽  
Satellite Orbit ◽  
Major Axis ◽  
Scale Height ◽  
Semi Major Axis ◽  
Relative Variation ◽  
Air Density ◽  
The Earth ◽  
Point Data

The theory previously developed for the changes in the perigee distance and semi-major axis of a satellite orbit due to air drag is extended to enable the air-density profile (i. e. its relative variation with height) to be derived from the motion of the orbit’s perigee. The solution is first obtained in terms of the change in perigee distance and then in terms of the change in the radius of the earth at the sub-perigee point. Data are analyzed by the two methods, leading to 39 (± 9) and 36 (± 15) km for the scale height in the 180 and 220 km altitude regions.

scholarly journals The impact of diurnal variations of air traffic on contrail radiative forcing

2007 ◽  
Vol 7 (12) ◽  
pp. 3153-3162 ◽  
Author(s):  
N. Stuber ◽  
P. Forster
Keyword(s):  
Radiative Forcing ◽  
Western Europe ◽  
Analysis Data ◽  
Air Traffic ◽  
Diurnal Variations ◽  
Night Time ◽  
The North ◽  
Framework Programme Project ◽  
Sky Conditions ◽  
The Impact

Abstract. We combined high resolution aircraft flight data from the EU Fifth Framework Programme project AERO2k with analysis data from the ECMWF's integrated forecast system to calculate diurnally resolved 3-D contrail cover. We scaled the contrail cover in order to match observational data for the Bakan area (eastern-Atlantic/western-Europe). We found that less than 40% of the global distance travelled by aircraft is due to flights during local night time. Yet, due to the cancellation of shortwave and longwave effects during daytime, night time flights contribute a disproportional 60% to the global annual mean forcing. Under clear sky conditions the night flights contribute even more disproportionally at 76%. There are pronounced regional variations in night flying and the associated radiative forcing. Over parts of the North Atlantic flight corridor 75% of air traffic and 84% of the forcing occurs during local night, whereas only 35% of flights are during local night in South-East Asia, yet these contribute 68% of the radiative forcing. In general, regions with a significant local contrail radiative forcing are also regions for which night time flights amount to less than half of the daily total of flights. Therefore, neglecting diurnal variations in air traffic/contrail cover by assuming a diurnal mean contrail cover can over-estimate the global mean radiative forcing by up to 30%.

scholarly journals GOMOS ozone profile validation using ground-based and balloon sonde measurements

2010 ◽  
Vol 10 (21) ◽  
pp. 10473-10488 ◽  
Author(s):  
J. A. E. van Gijsel ◽  
D. P. J. Swart ◽  
J.-L. Baray ◽  
H. Bencherif ◽  
H. Claude ◽  
...  
Keyword(s):  
Selection Criteria ◽  
Polar Region ◽  
Temporal Trend ◽  
Microwave Radiometer ◽  
Line Of Sight ◽  
Night Time ◽  
Latitudinal Dependence ◽  
Ozone Profile ◽  
The Tropics ◽  
Level 2

Abstract. The validation of ozone profiles retrieved by satellite instruments through comparison with data from ground-based instruments is important to monitor the evolution of the satellite instrument, to assist algorithm development and to allow multi-mission trend analyses. In this study we compare ozone profiles derived from GOMOS night-time observations with measurements from lidar, microwave radiometer and balloon sonde. Collocated pairs are analysed for dependence on several geophysical and instrument observational parameters. Validation results are presented for the operational ESA level 2 data (GOMOS version 5.00) obtained during nearly seven years of observations and a comparison using a smaller dataset from the previous processor (version 4.02) is also included. The profiles obtained from dark limb measurements (solar zenith angle >107°) when the provided processing flag is properly considered match the ground-based measurements within ±2 percent over the altitude range 20 to 40 km. Outside this range, the pairs start to deviate more and there is a latitudinal dependence: in the polar region where there is a higher amount of straylight contamination, differences start to occur lower in the mesosphere than in the tropics, whereas for the lower part of the stratosphere the opposite happens: the profiles in the tropics reach less far down as the signal reduces faster because of the higher altitude at which the maximum ozone concentration is found compared to the mid and polar latitudes. Also the bias is shifting from mostly negative in the polar region to more positive in the tropics Profiles measured under "twilight" conditions are often matching the ground-based measurements very well, but care has to be taken in all cases when dealing with "straylight" contaminated profiles. For the selection criteria applied here (data within 800 km, 3 degrees in equivalent latitude, 20 h (5 h above 50 km) and a relative ozone error in the GOMOS data of 20% or less), no dependence was found on stellar magnitude, star temperature, nor the azimuth angle of the line of sight. No evidence of a temporal trend was seen either in the bias or frequency of outliers, but a comparison applying less strict data selection criteria might show differently.

scholarly journals LOFAR observations of the quiet solar corona

2018 ◽  
Vol 614 ◽  
pp. A54 ◽  
Author(s):  
C. Vocks ◽  
G. Mann ◽  
F. Breitling ◽  
M. M. Bisi ◽  
B. Dąbrowski ◽  
...  
Keyword(s):  
Radio Emission ◽  
Solar Corona ◽  
Density Profile ◽  
Extreme Ultraviolet ◽  
Low Frequency ◽  
Scale Height ◽  
Solar Radio Emission ◽  
Radial Magnetic Field ◽  
Brightness Temperatures ◽  
Hydrostatic Model

Context. The quiet solar corona emits meter-wave thermal bremsstrahlung. Coronal radio emission can only propagate above that radius, Rω, where the local plasma frequency equals the observing frequency. The radio interferometer LOw Frequency ARray (LOFAR) observes in its low band (10–90 MHz) solar radio emission originating from the middle and upper corona. Aims. We present the first solar aperture synthesis imaging observations in the low band of LOFAR in 12 frequencies each separated by 5 MHz. From each of these radio maps we infer Rω, and a scale height temperature, T. These results can be combined into coronal density and temperature profiles. Methods. We derived radial intensity profiles from the radio images. We focus on polar directions with simpler, radial magnetic field structure. Intensity profiles were modeled by ray-tracing simulations, following wave paths through the refractive solar corona, and including free-free emission and absorption. We fitted model profiles to observations with Rω and T as fitting parameters. Results. In the low corona, Rω < 1.5 solar radii, we find high scale height temperatures up to 2.2 × 106 K, much more than the brightness temperatures usually found there. But if all Rω values are combined into a density profile, this profile can be fitted by a hydrostatic model with the same temperature, thereby confirming this with two independent methods. The density profile deviates from the hydrostatic model above 1.5 solar radii, indicating the transition into the solar wind. Conclusions. These results demonstrate what information can be gleaned from solar low-frequency radio images. The scale height temperatures we find are not only higher than brightness temperatures, but also than temperatures derived from coronograph or extreme ultraviolet (EUV) data. Future observations will provide continuous frequency coverage. This continuous coverage eliminates the need for local hydrostatic density models in the data analysis and enables the analysis of more complex coronal structures such as those with closed magnetic fields.

scholarly journals Mesospheric Ozone Density Profile in the Polar Region.

1997 ◽  
Vol 49 (5) ◽  
pp. 675-688 ◽  
Author(s):  
Hiromasa Yamamoto ◽  
Ken-ichi Yajima ◽  
Hiroyuki Sekiguchi ◽  
Tadao Makino
Keyword(s):  
Density Profile ◽  
Polar Region ◽  
Mesospheric Ozone

scholarly journals Towards Real-Time Density Profile Reconstruction With Cuda

2016 ◽  
Author(s):  
Pedro Carvalho ◽  
Diogo R. Ferreira ◽  
Horácio Fernandes ◽  
Luís Meneses
Keyword(s):  
Real Time ◽  
Density Profile ◽  
Profile Reconstruction ◽  
Time Density

scholarly journals Global contrail radiative forcing and the impact of diurnal variations of air the impact of diurnal variations of air

2006 ◽  
Vol 6 (5) ◽  
pp. 9123-9149
Author(s):  
N. Stuber ◽  
P. Forster
Keyword(s):  
Optical Depth ◽  
Radiative Forcing ◽  
Western Europe ◽  
Analysis Data ◽  
Diurnal Variations ◽  
Night Time ◽  
Model Calculations ◽  
Framework Programme Project ◽  
Year 2000 ◽  
The Impact

Abstract. We combined high resolution aircraft flight data from the EU Fifth Framework Programme project AERO2k with analysis data from the ECMWF's integrated forecast system to calculate diurnally resolved 3-D contrail cover. Calibrating for the 1992 contrail cover in the Bakan area (eastern-Atlantic/western-Europe), we obtained a global, annual mean contrail cover due to persistent, line-shaped contrails of 0.04%. Adopting a contrail visible optical depth of 0.1, this contrail cover results in a global, annual mean radiative forcing of 2.0 mW/m2 for all-sky and 2.1 mW/m2 for clear sky conditions. Less than 40% of the global distance travelled by aircraft is due to flights during local night time. Yet, due to the cancellation of shortwave and longwave effects during daytime, night-flights contribute a disproportional 60 to 76% to the annual mean forcing. In general, regions with a significant local contrail radiative forcing are also regions for which night time flights amount to less than half of the daily total of flights. Neglecting diurnal variations in air traffic/contrail cover by assuming a diurnal mean contrail cover can therefore increase the global mean radiative forcing by up to 30%. Scaling the 1992 forcing for the year 2000 fuel usage and accounting for differences in contrail optical depth, our forcing estimate is at the lower end but within the range of the most recent results. This reinforces the finding that some earlier published estimates of contrail radiative forcing are likely to be too large. Our study builds confidence in the calculation of contrail radiative forcing. Once the amount and optical properties of contrails are known there is relatively little uncertainty about their radiative effects. However, global model calculations of contrail radiative forcing crucially rely on scaling their contrail cover with observations. We therefore see the urgent need for an update of area mean contrail cover values derived from multi-year analyses of observational data.

scholarly journals Temperature decadal trends, and their relation to diurnal variations in the lower thermosphere, stratosphere, and mesosphere, based on measurements from SABER on TIMED

2020 ◽  
Author(s):  
Frank T. Huang ◽  
Hans G. Mayr
Keyword(s):  
Local Time ◽  
Lower Thermosphere ◽  
3D Models ◽  
Diurnal Variations ◽  
Time Span ◽  
Local Times ◽  
Night Time ◽  
Temperature Trends ◽  
Lidar Measurements ◽  
Thermal Tides

Abstract. We have derived the behavior of decadal temperature trends over the 24 hours of local time, based on zonal averages of SABER data, years 2012 to 2014, 20 to 100 km, within 48° of the equator. Similar results have not been available previously. We find that the temperature trends, based on zonal mean measurements at a fixed local time, can be different from those based on measurements made at a different fixed local time. The trends can vary significantly in local time, even from hour to hour. This agrees with some findings based on night-time lidar measurements. This knowledge is relevant because the large majority of temperature measurements, especially in the stratosphere, are made by instruments on sun-synchronous operational satellites which measure at only one or two fixed local times, for the duration of their missions. In these cases, the zonal mean trends derived from various satellite data are tied to the specific local times at which each instrument samples the data, and the trends are then also biased by the local time. Consequently, care is needed in comparing trends based on various measurements with each other, unless the data are all measured at the same local time. A similar caution is needed when comparing with models, since the zonal means from 3D models reflect averages over both longitude and the 24 hours of local time. Consideration is also needed in merging data from various sources to produce generic, continuous longer-term records. Diurnal variations of temperature themselves, in the form of thermal tides, are well known, and are due to absorption of solar radiation. We find that at least part of the reason that temperature trends are different for different local times is that the amplitudes and phases of the tides themselves follow trends over the same time span of the data. Much of past efforts have focused on the temperature values with local time when merging data from various sources, and on the effect of unintended satellite orbital drifts, which result in drifting local times at which the temperatures are measured. However, the effect of local time on trends has not been well researched. We also derive estimates of trends by simulating the drift of local time due to drifting orbits. Our comparisons with results found by others (AMSU, lidar) are favorable and informative. They may explain at least in part, the bridge between results based on daytime AMSU data and night time lidar measurements. However, these examples do not a pattern make, and more comparisons and study are needed.

scholarly journals Electron Densities and Scale Heights in the Mid-latitude Topside Ionosphere

1967 ◽  
Vol 20 (4) ◽  
pp. 401 ◽  
Author(s):  
PL Dyson
Keyword(s):  
Electron Density ◽  
Northern Hemisphere ◽  
Scale Height ◽  
Topside Ionosphere ◽  
Electron Densities ◽  
Night Time ◽  
Transition Level ◽  
Latitude Region ◽  
Latitudinal Variations

The diurnal and latitudinal variations of electron density and plasma scale height in the topside ionosphere during summer and winter have been calculated from Alouette I ionograms recorded at Woomera. The electron density behaviour is anomalous in that the winter night-time values are generally as large or larger than those occurring during the day. At heights near 1000 km the winter night-time values are greater than those for night-time summer. The behaviour of the scale height is very similar to that reported by others for the mid-latitude region of the northern hemisphere and implies that at night-time the transition level from 0+ to lighter ions occurs at heights of about 550 km in summer and 500 km in winter.

Near-circular orbits within a rotating oblate atmosphere with a diurnal variation in density and variable density scale height

1992 ◽  
Vol 437 (1900) ◽  
pp. 461-474 ◽  
Keyword(s):  
Diurnal Variation ◽  
Density Profile ◽  
Earth Satellite ◽  
Variable Density ◽  
Scale Height ◽  
Circular Orbits ◽  
Air Drag ◽  
Orbital Revolution ◽  
Density Scale

The motion of an Earth satellite is considered within an oblate atmosphere with a diurnally varying density profile and a variable density scale height. Expressions are derived which represent the changes of parameters specifying the eccentricity and argument of perigee during one complete orbital revolution. The influence of air drag on near-circular orbits is examined and an insight is gained into the reinforcing or counterbalancing effects of atmospheric oblateness and variable density scale height.

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