Prediction skill of monthly SST in the North Atlantic Ocean in NCEP Climate Forecast System version 2   总被引：1，自引：0，他引：1  

Zeng-Zhen Hu  Arun Kumar  Bohua Huang  Wanqiu Wang  Jieshun Zhu  Caihong Wen 《Climate Dynamics》2013,40(11-12):2745-2759

This work evaluates the skill of retrospective predictions of the second version of the NCEP Climate Forecast System (CFSv2) for the North Atlantic sea surface temperature (SST) and investigates the influence of El Niño-Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) on the prediction skill over this region. It is shown that the CFSv2 prediction skill with 0–8 month lead displays a “tripole”-like pattern with areas of higher skills in the high latitude and tropical North Atlantic, surrounding the area of lower skills in the mid-latitude western North Atlantic. This “tripole”-like prediction skill pattern is mainly due to the persistency of SST anomalies (SSTAs), which is related to the influence of ENSO and NAO over the North Atlantic. The influences of ENSO and NAO, and their seasonality, result in the prediction skill in the tropical North Atlantic the highest in spring and the lowest in summer. In CFSv2, the ENSO influence over the North Atlantic is overestimated but the impact of NAO over the North Atlantic is not well simulated. However, compared with CFSv1, the overall skills of CFSv2 are slightly higher over the whole North Atlantic, particularly in the high latitudes and the northwest North Atlantic. The model prediction skill beyond the persistency initially presents in the mid-latitudes of the North Atlantic and extends to the low latitudes with time. That might suggest that the model captures the associated air-sea interaction in the North Atlantic. The CFSv2 prediction is less skillful than that of SSTA persistency in the high latitudes, implying that over this region the persistency is even better than CFSv2 predictions. Also, both persistent and CFSv2 predictions have relatively low skills along the Gulf Stream.  相似文献   

PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope     

Arun Naidu  Bhal Chandra Joshi  P. K. Manoharan  M. A. Krishnakumar 《Experimental Astronomy》2015,39(2):319-341

  相似文献   

Anomalous land surface temperature and outgoing long-wave radiation observations prior to earthquakes in India and Romania   总被引：2，自引：1，他引：1  

Vineeta Rawat  Arun K. Saraf  Josodhir Das  Kanika Sharma  Yazdana Shujat 《Natural Hazards》2011,59(1):33-46

Cumulative stress energy in an earthquake preparation zone under operating tectonic force manifests various observable signs of the impending earthquake, i.e., earthquake precursors. This energy transformation may result in enhanced transient thermal infrared (TIR) emission, which can be detected through satellites equipped with thermal sensors like AVHRR (NOAA), MODIS (Terra/Aqua). This paper presents observations made using NOAA-AVHRR data–derived land surface temperature (LST) and outgoing long-wave radiation (OLR) values in case of two moderate earthquakes (22 July 2007, Yamnotri earthquake, India and 27 October 2004, Vrancea earthquake, Romania) using anomalous TIR signals as reflected in LST rise and high OLR values can be seen conspicuously and following similar growth pattern spatially and temporally. In both the cases, data analysis revealed a transient thermal infrared rise in LST ranging 5–10°C around epicentral areas. The thermal anomalies started developing about 7–8 days prior to the main event depending upon the magnitude and focal depth and disappeared after the main shock. Similarly, the OLR values ~30–45 W/m² higher than the normal were observed 7–8 days prior to the main event. The rise in LST can be attributed to enhanced greenhouse gas emission from the squeezed rock pore spaces and/or to the activation of p-holes in stressed rock volume and their further recombination at rock-air interface. OLR is temperature and humidity dependent, and any change in these variables may be responsible for anomalous OLR values.  相似文献   

Halo ejection in distant radio galaxies: jet feedback in massive galaxy formation     

Michael A. Dopita  Michiel Reuland  Wil van Breugel  Wim de Vries  S. A. Stanford  Huub Röttgering  George Miley  Bram Venemans  Hy Spinrad  Steve Dawson  Arjun Dey  Mark Lacy  Daniel Stern  Andrew Bunker 《Astrophysics and Space Science》2007,311(1-3):305-309

We present results from a Keck optical and near IR spectroscopic study of the giant emission line halos of the z>3 High Redshift Radio Galaxies (HiZRGs) 4C 41.17, 4C 60.07 and B2 0902+34. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s⁻¹ and velocity shears consistent with rotation. The inner regions contain shocked, clumpy cocoons of gas closely associated with the radio lobes with disturbed kinematics and expansion velocities and/or velocity dispersions >1000 km s⁻¹. We also find evidence for the ejection of chemically enriched material in 4C 41.17 up to a distance of ∼60 kpc along the radio-axis. We infer that these HiZRGs are undergoing a final jet-induced phase of star formation with the ejection of most of their interstellar medium before evolving to become “red and dead” Elliptical galaxies.  相似文献   

Vertical profiles of aerosol black carbon in the atmospheric boundary layer over a tropical coastal station: Perturbations during an annular solar eclipse     

S. Suresh Babu  V. Sreekanth  K. Krishna Moorthy  Mannil Mohan  N.V.P. Kirankumar  D. Bala Subrahamanyam  Mukunda M. Gogoi  Sobhan Kumar Kompalli  Naseema Beegum  Jai Prakash Chaubey  V.H. Arun Kumar  Ravi K. Manchanda 《Atmospheric Research》2011,99(3-4):471-478

Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer (ABL) over a tropical coastal station, Trivandrum have been examined on two days using an aethalometer attached to a tethered balloon. One of these days (15th January, 2010) coincided with a (annular) solar eclipse, the longest of this century at this location, commenced at 11:05 local time and ended by 15:05, lasting for 7 min and 15 s (from 13:10:42), with its maximum contact occurring at ~ 13:14 IST with ~ 92% annularity, thereby providing an opportunity to understand the eclipse induced perturbations. Concurrent measurements of the ABL parameters such as air temperature, relative humidity and pressure were also made on these days to describe the response of the ABL to the eclipse. BC profiles, in general, depicted similar features up to an altitude of ~ 200 m on the eclipse day and control day, above which it differed conspicuously with profiles on eclipse day showing increasingly lower concentration as we moved to higher altitudes. Examination of the meteorological profiles showed that the altitude of maximum convection rapidly fell down during the eclipse period compared to that on control day indicating a rather shallow convection on eclipse day. Comparison of diurnal variations of BC at the surface level showed that the rate of decrease in BC during daytime on the eclipse day was smaller than that on the control day due to the reduced convection, shallow ABL and consequent reduction in the ventilation coefficient. Moreover the time of the nocturnal increase has advanced by ~ 1:30 h on the eclipse day, occurred at around 19:30 IST in contrast to all the other days of January 2010, where this increase usually occur well after 20:30 IST, with a mean value of 21:00 IST. This is attributed to the weak sea-breeze penetration during the eclipse day, which led to an early onset of the land breeze.  相似文献   

Against mono-consequentialism: Multiple outcomes and their drivers in social–ecological systems     

Arun Agrawal  Ashwini Chhatre   《Global Environmental Change》2011,21(1):1-3

  相似文献   

Reconstruction of Antarctic climate change using ice core proxy records from the coastal Dronning Maud Land,East Antarctica     

Meloth Thamban  C. M. Laluraj  Sushant S. Naik  Arun Chaturvedi 《Journal of the Geological Society of India》2011,78(1):19-29

Antarctic ice core records have provided unprecedented information on past climatic changes and forcing factors on decadal to millennial timescales. The glaciochemical and stable isotope records of a shallow ice core from the coastal Dronning Maud Land (East Antarctica) were used here to reconstruct the coastal Antarctic environmental variability during the past ∼470 years. Sea salt ion data indicate a significant additional contribution of chloride ions compared to sea water values, possibly through atmospheric scavenging. The nitrate (NO₃ ⁻) profile exhibit significant temporal shifts than that of the sulphate (SO₄ ²⁻), with a major shift around 1750 AD. The changes in NO₃ ⁻ record are synchronous with the proxy record of solar activity (¹⁰Be profile from a South Pole ice core), suggesting enhanced NO₃ ⁻ values during periods of reduced solar activity like the Dalton Minimum (∼1790–1830 AD) and Maunder Minimum (∼1640–1710 AD). The δ¹⁸O records reveal that the more negative δ¹⁸O values were coeval with several events of increased NO₃ ⁻ concentrations, suggesting enhanced preservation of NO₃ ⁻ during periods of reduced air temperatures. The δ¹⁸O and δD records of the core also suggest significant short-term and long-tem variability with more negative values indicating relatively lower air temperatures prior to 1715 AD. The δ¹⁸O records also revealed a significant warming of 2.7°C for the past 470 years, with a warming of ∼0.6°C per century.  相似文献   

Is there lower limit to velocity or velocity change?     

B. N. Sreenath  Kenath Arun  C. Sivaram 《Astrophysics and Space Science》2013,345(1):209-211

Here we explore the possibility of a lower limit to velocity or velocity change which is 20 orders of magnitude smaller than the speed of light and explore the various observable signatures including those in cosmic rays and gamma ray bursts.  相似文献   

Why were some La Niñas followed by another La Niña?     

Zeng-Zhen Hu  Arun Kumar  Yan Xue  Bhaskar Jha 《Climate Dynamics》2014,42(3-4):1029-1042

This paper investigates why some La Niña events are followed by another La Niña and some others are not. We propose two preconditions that result in continuation of a La Niña. The first one is that La Niña must be a strong event (a major La Niña). This ensures that the reflected Rossby wave signal at the eastern boundary of the Pacific has a strong westward propagating cold ocean temperature anomaly over the off-equatorial region. The off-equator cold anomaly may not be conducive to the equatorial recharge process, and as a result, may favor the persistence of cold ocean subsurface temperature anomaly and prevent the transition from La Niña to El Niño. The second precondition is whether there are eastward propagating downwelling Kelvin waves during the decay phase of a major La Niña. Eastward propagating downwelling Kelvin waves could lead to demise for a tendency for a follow-up La Niña. The equatorial Kelvin wave activities are associated with fluctuations of surface wind in the equatorial far-western Pacific. The analysis suggests that both the surface wind in the equatorial far-western Pacific and the recharge/discharge of the equatorial Pacific are indicators for occurrence or no occurrence of a follow-up La Niña event.  相似文献   

A Comparative Analysis on the Applicability of Entropy in Remote Sensing     

P. V. Arun 《Journal of the Indian Society of Remote Sensing》2014,42(1):217-226

Entropy is the measure of uncertainty in any data and is adopted for maximisation of mutual information in many remote sensing operations. The availability of wide entropy variations motivated us for an investigation over the suitability preference of these versions to specific operations. The popular available versions like Tsalli’s, Shannon’s, and Renyi’s entropies have been analysed in context of various remote sensing operations namely thresholding, clustering and registration. These methodologies have been evaluated with reference to the study area using different statistical parameters. Renyi’s entropy has been found to be suitable for image registration purpose followed by Tsalli’s and Shannon; whereas Tsalli’s entropy has been found preferable for thresholding and clustering.  相似文献