scholarly journals On the use of outgoing longwave radiation data in incorporating divergent part of the wind in analysis

MAUSAM ◽  
2021 ◽  
Vol 43 (1) ◽  
pp. 21-28
Author(s):  
P. L. KULKARNI ◽  
D. R. TALWALKAR ◽  
SATHY NAIR ◽  
S. G. NARKHEDKAR ◽  
S. RAJAMANI
Keyword(s):  
Stream Function ◽  
Velocity Potential ◽  
Grid Point ◽  
Longwave Radiation ◽  
Initial Guess ◽  
Divergent Part ◽  
Interpolation Scheme ◽  
Rotational Part ◽  
Point Data ◽  
The Relationship

In the present study, kinematic divergence computed using ECMWF grid point data at 850 hPa  is enhanced by  using the relationship between OLR and divergence. This new enhanced divergence is used to  compute the velocity potential and then, the divergence part of the wind is obtained from velocity potetial. To obtain the rotational part of wind, we computed the vorticity from wind data, and subsequently stream function and obtained and the rotational part of the wind from the stream function. The total wind is the combination of divergent part obtained from modified velocity potential (using OLR data) and rotational part from unmodified stream function. This total wind field is used as initial guess for univariate objective analysis by optimum interpolation scheme so that Initial Guess field contained the more realistic divergent part of the wind. Consequently, the analysed field also will contain the divergent part of the wind.

Contracting ducts of finite length

1951 ◽  
Vol 2 (4) ◽  
pp. 254-271 ◽  
Author(s):  
L. G. Whitehead ◽  
L. Y. Wu ◽  
M. H. L. Waters
Keyword(s):  
Stream Function ◽  
Finite Length ◽  
Velocity Potential ◽  
Three Dimensional ◽  
Relaxation Method ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Hodograph Plane ◽  
Two Dimensional Flow ◽  
Working Section

SummmaryA method of design is given for wind tunnel contractions for two-dimensional flow and for flow with axial symmetry. The two-dimensional designs are based on a boundary chosen in the hodograph plane for which the flow is found by the method of images. The three-dimensional method uses the velocity potential and the stream function of the two-dimensional flow as independent variables and the equation for the three-dimensional stream function is solved approximately. The accuracy of the approximate method is checked by comparison with a solution obtained by Southwell's relaxation method.In both the two and the three-dimensional designs the curved wall is of finite length with parallel sections upstream and downstream. The effects of the parallel parts of the channel on the rise of pressure near the wall at the start of the contraction and on the velocity distribution across the working section can therefore be estimated.

scholarly journals The Relationship Between Cloud Cover and Outgoing Longwave Radiation in the Southern of Vietnam

2018 ◽  
Vol 34 (1S) ◽  
Author(s):  
Chu Thi Thu Huong ◽  
Bui Thi Hop ◽  
Tran Dinh Linh ◽  
Vu Thanh Hang
Keyword(s):  
Spatial Distribution ◽  
Rainy Season ◽  
Outgoing Longwave Radiation ◽  
Cloud Cover ◽  
Temporal Evolution ◽  
El Nino ◽  
Longwave Radiation ◽  
Downward Trend ◽  
La Nina ◽  
The Relationship

Abstract: Based on the data that has the resolution is 1,00×1,00of the Outgoing Longwave Radiation (OLR) and the cloud cover from NCEP/NCAR in the 1981 – 2012 period, the relationship between the cloud cover and the OLR in the Southern of Vietnam wasinvestigated when analyze and compare the spatial distribution, temporal evolution and their correlation. The results show that the characteristics of the spatial distribution and the year cycle of cloud cover and OLR are inversely correlated. The region or time that the cloud cover is great, the OLR is small and vice versa. In the Southern of Vietnam, the OLR value isgreatest(or smallest) in the dry (or rainy) season and in the El-Nino (La-Nina) years. In addition, during the 1981-2012period, the OLR in this region shows a downward trend about 3.6 W/m2/decade, while the cloud cover tends to increase by 0.2%/decade. Keywords: Cloud cover, Outgoing Longwave Radiation, the Southern of Vietnam.

The instabilities of gravity waves of finite amplitude in deep water I. Superharmonics

1978 ◽  
Vol 360 (1703) ◽  
pp. 471-488 ◽  
Keyword(s):  
Stream Function ◽  
Gravity Waves ◽  
Velocity Potential ◽  
Travelling Waves ◽  
Normal Modes ◽  
Phase Speed ◽  
Finite Amplitude ◽  
Fundamental Wave ◽  
Wave Steepness ◽  
Horizontal Scale

In this paper we embark on a calculation of all the normal-mode perturbations of nonlinear, irrotational gravity waves as a function of the wave steepness. The method is to use as coordinates the stream-function and velocity potential in the steady, unperturbed wave (seen in a reference frame moving with the phase speed) together with the time t. The dependent quantities are the cartesian displacements and the perturbed stream function at the free surface. To begin we investigate the ‘superharmonics’, i.e. those perturbations having the same horizontal scale as the fundamental wave, or less. When the steepness of the fundamental is small, the normal modes take the form of travelling waves superposed on the basic nonlinear wave. As the steepness increases the frequency of each perturbation tends generally to be diminished. At a steepness ak ≈ 0.436 it appears that the two lowest modes coalesce and an instability arises. There is evidence that this critical steepness corresponds precisely with the steepness at which the phase velocity is a maximum, considered as a function of ak. The calculations are facilitated by the discovery of some new identities between the coefficients in Stokes’s expansion for waves of finite amplitude.

scholarly journals Application of Latitude Stripe Division in Satellite Constellation Coverage to Ground

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Maocai Wang ◽  
Xin Luo ◽  
Guangming Dai ◽  
Xiaoyu Chen
Keyword(s):  
Orbital Period ◽  
High Efficiency ◽  
Classical Method ◽  
Grid Point ◽  
Spherical Geometry ◽  
Optimized Design ◽  
Target Region ◽  
Satellite Constellation ◽  
Orbital Periods ◽  
The Relationship

Grid point technique is a classical method in computing satellite constellation coverage to the ground regions. Aiming at improving the low computational efficiency of the conventional method, a method using latitude stripe division is proposed, which has high efficiency, and we name it latitude stripe method. After dividing the target region into several latitude stripes, the coverage status of each latitude stripe is computed by means of the spherical geometry relationship in the first orbital period. The longitude coverage intervals in the remaining orbital periods are computed by sliding the coverage status in the first orbital period. Based on this method, the instantaneous and cumulative coverage in simulation time can be calculated more efficiently. As well, the relationship between the cumulative coverage and altitude can be computed fast by this method, which could be used in the optimized design of repeating sun-synchronous orbits. The comparison between the conventional grid point method and the latitude stripe method shows that the latitude stripe method has high efficiency and accuracy. Through various case studies, the optimization in repeating sun-synchronous orbits design is successfully represented.

scholarly journals Energy Balance Calculations for the Ablation Period 1982 at Vernagtferner. Oetztal Alps

1985 ◽  
Vol 6 ◽  
pp. 158-160 ◽  
Author(s):  
Heidi Escher-Vetter
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Radiation Balance ◽  
Sensible Heat ◽  
The Individual ◽  
The Relationship ◽  
Climatic Pattern

In this paper, some features of energy balance terms will be discussed in respect to the melting capacity available at the surface of Vernagtferner in the Oetztal Alps. The climatic pattern of summer 1982 is described, then the method of calculating individual terms (shortwave and longwave radiation balance, sensible and latent heat flux) from records of radiation, air temperature, humidity and wind. The results of these calculations are discussed for ice, firn and snow areas of the glacier. In particular the relationship between the four terms is shown for 15 July 1982, the day with highest meltwater production in 1982. These values are then compared with the maximum values of the individual terms, showing that the highest meltwater production is caused by the combination of quite high values of the individual terms, but not of the absolutely highest ones. The importance of sensible heat flux for meltwater production in 1982 is discussed: comparison between meltwater production for the whole summer and measured runoff shows reasonable accordance.

scholarly journals A Survey on the Relationship between Ocean Subsurface Temperature and Tropical Cyclone over the Western North Pacific

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Difu Sun ◽  
Junqiang Song ◽  
Kaijun Ren ◽  
Xiaoyong Li ◽  
Guangjie Wang
Keyword(s):  
Tropical Cyclone ◽  
Water Temperature ◽  
Negative Correlation ◽  
North Pacific ◽  
Western North Pacific ◽  
Vertical Wind Shear ◽  
Longwave Radiation ◽  
Subsurface Water ◽  
Subsurface Temperature ◽  
The Relationship

The relationship between ocean subsurface temperature and tropical cyclone (TC) over the western North Pacific (WNP) is studied based on the TC best-track data and global reanalysis data during the period of 1948–2012. Here the TC frequency (TCF), lifespan, and genesis position of TCs are analysed. A distinctive negative correlation between subsurface water temperature and TCF is observed, especially the TCF in the southeastern quadrant of the WNP (0–15°N, 150–180°E). According to the detrended subsurface temperature anomalies of the 125 m depth layer in the main TC genesis area (0–30°N, 100–180°E), we selected the subsurface cold and warm years. During the subsurface cold years, TCs tend to have a longer mean lifespan and a more southeastern genesis position than the subsurface warm years in general. To further investigate the causes of this characteristic, the TC genesis potential indexes (GPI) are used to analyse the contributions of environmental factors to TC activities. The results indicate that the negative correlation between subsurface water temperature and TCF is mainly caused by the variation of TCF in the southeastern quadrant of the WNP, where the oceanic and atmospheric environments are related to ocean subsurface conditions. Specifically, compared with the subsurface warm years, there are larger relative vorticity, higher relative humidity, smaller vertical wind shear, weaker net longwave radiation, and higher ocean mixed layer temperature in the southeastern quadrant during cold years, which are all favorable for genesis and development of TC.

A Modified Multivariate Madden–Julian Oscillation Index Using Velocity Potential

2013 ◽  
Vol 141 (12) ◽  
pp. 4197-4210 ◽  
Author(s):  
Michael J. Ventrice ◽  
Matthew C. Wheeler ◽  
Harry H. Hendon ◽  
Carl J. Schreck ◽  
Chris D. Thorncroft ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Velocity Potential ◽  
Longwave Radiation ◽  
Warm Pool ◽  
Boreal Summer ◽  
Madden Julian Oscillation ◽  
Systematic Analysis ◽  
Planetary Scale ◽  
Daily Data ◽  
The Indian Ocean

Abstract A new Madden–Julian oscillation (MJO) index is developed from a combined empirical orthogonal function (EOF) analysis of meridionally averaged 200-hPa velocity potential (VP200), 200-hPa zonal wind (U200), and 850-hPa zonal wind (U850). Like the Wheeler–Hendon Real-time Multivariate MJO (RMM) index, which was developed in the same way except using outgoing longwave radiation (OLR) data instead of VP200, daily data are projected onto the leading pair of EOFs to produce the two-component index. This new index is called the velocity potential MJO (VPM) indices and its properties are quantitatively compared to RMM. Compared to the RMM index, the VPM index detects larger-amplitude MJO-associated signals during boreal summer. This includes a slightly stronger and more coherent modulation of Atlantic tropical cyclones. This result is attributed to the fact that velocity potential preferentially emphasizes the planetary-scale aspects of the divergent circulation, thereby spreading the convectively driven component of the MJO’s signal across the entire globe. VP200 thus deemphasizes the convective signal of the MJO over the Indian Ocean warm pool, where the OLR variability associated with the MJO is concentrated, and enhances the signal over the relatively drier longitudes of the equatorial Pacific and Atlantic. This work provides a useful framework for systematic analysis of the strengths and weaknesses of different MJO indices.

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