The ocean-atmosphere response to wind-induced thermocline changes in the tropical South Western Indian Ocean

In the Indian Ocean basin the sea surface temperatures (SSTs) are most sensitive to changes in the oceanic depth of the thermocline in the region of the Seychelles Dome. Observational studies have suggested that the strong SST variations in this region influence the atmospheric evolution around the basin, while its impact could extend far into the Pacific and the extra-tropics. Here we study the adjustments of the coupled atmosphere-ocean system to a winter shallow doming event using dedicated ensemble simulations with the state-of-the-art EC-Earth climate model. The doming creates an equatorial Kelvin wave and a pair of westward moving Rossby waves, leading to higher SST 1–2 months later in the Western equatorial Indian Ocean. Atmospheric convection is strengthened and the Walker circulation responds with reduced convection over Indonesia and cooling of the SST in that region. The Pacific warm pool convection shifts eastward and an oceanic Kelvin wave is triggered at thermocline depth. The wave leads to an SST warming in the East Equatorial Pacific 5–6 months after the initiation of the Seychelles Dome event. The atmosphere responds to this warming with weak anomalous atmospheric convection. The changes in the upper tropospheric divergence in this sequence of events create large-scale Rossby waves that propagate away from the tropics along the atmospheric waveguides. We suggest to repeat these types of experiments with other models to test the robustness of the results. We also suggest to create the doming event in June so that the East-Pacific warming occurs in November when the atmosphere is most sensitive to SST anomalies and El Niño could possibly be triggered by the doming event under suitable conditions

Moisture variability over the Indo-Pacific region and its influence on the Indian summer monsoon rainfall

The Indo-Pacific Ocean (i.e. region between 30°E and 150°E) has been experiencing a warming since the 1950s. At the same time, the large-scale summer monsoon rainfall over India and the moisture over the East Africa/Arabian Sea are both decreasing. In this study, we intend to investigate how the decrease of moisture over the East Africa/Arabian Sea is related to the Indo-Pacific Ocean warming and how this could affect the variability of the Indian summer monsoon rainfall. We performed the analysis for the period 1951–2012 based on observed precipitation, sea surface temperature and atmospheric reanalysis products and we verified the robustness of the result by comparing different datasets. The decreasing trend of moisture over the East Africa/Arabian Sea coincides with an increasing trend of moisture over the western Pacific region. This is accompanied by the strengthening (weakening) of the upward motion over the western Pacific (East Africa/Arabian Sea) that, consequently, contributes to modulate the western Pacific-Indian Ocean Walker circulation. At the same time, the low-level westerlies are weakening over the peninsular India, thus contributing to the reduction of moisture transport towards India. Therefore, rainfall has decreased over the Western Ghats and central-east India. Contrary to previous decades, since 2003 moisture over the East Africa/Arabian Sea started to increase and this is accompanied by the strengthening of convection due to increased warming of sea surface temperature over the western Arabian Sea. Despite this moisture increase over the Arabian Sea, we found that moisture transport is still weakening over the Indian landmass in the very recent decade and this has been contributing to the decreased precipitation over the northeast India and southern part of the Western Ghats

INCLUSIVE TRANSVERSE-MOMENTUM DISTRIBUTIONS OF CHARGED-PARTICLES IN DIFFRACTIVE AND NON-DIFFRACTIVE PHOTOPRODUCTION AT HERA RID B-9165-2008 RID C-5889-2009 RID A-4818-2008 RID C-1693-2008

Inclusive transverse momentum spectra of charged particles in photoproduction events in the laboratory pseudorapidity range -1.2 < eta < 1.4 have been measured up to P-T = 8 GeV using the ZEUS detector. Diffractive and non-diffractive reactions have been selected with an average gamma p centre of mass (c.m.) energy of (W) = 180 GeV. For diffractive reactions, the p(T) spectra of the photon dissociation events have been measured in two intervals of the dissociated photon mass with mean values (M(X)) = 5 GeV and 10 GeV. The inclusive transverse momentum spectra fall exponentially in the low p(T) region. The non-diffractive data p show a pronounced high p(T) tail departing from the exponential shape. The p(T) distributions are compared to lower energy photoproduction data and to hadron-hadron collisions at a similar c.m. energy. The data are also compared to the results of a next-to-leading order QCD calculation

EXTRACTION OF THE GLUON DENSITY OF THE PROTON AT X RID B-9165-2008 RID C-5889-2009 RID A-4818-2008 RID C-1693-2008

The gluon momentum density xg(x, Q(2)) of the proton was extracted at Q(2) = 20 GeV2 for small values of x between 4 x 10(-4) and 10(-2) from the scaling violations of the proton structure function F-2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F-2 at low x constrained by measurements from NMC at larger x; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x

MEASUREMENT OF MULTIPLICITY AND MOMENTUM SPECTRA IN THE CURRENT FRAGMENTATION REGION OF THE BREIT FRAME AT HERA RID B-9165-2008 RID C-5889-2009 RID A-4818-2008 RID C-1693-2008

Charged particle production has been measured in Deep Inelastic Scattering (DIS) events using the ZEUS detector over a large range of Q(2) from 10 to 1280 GeV2 The evolution with Q of the charged multiplicity and scaled momentum has been investigated in the current fragmentation region of the Breit frame. The data are used to study QCD coherence effects in DIS and are compared with corresponding e(+)e(-) data in order to test the universality of quark fragmentation

MEASUREMENT OF MULTIPLICITY AND MOMENTUM SPECTRA IN THE CURRENT FRAGMENTATION REGION OF THE BREIT FRAME AT HERA

Charged particle production has been measured in Deep Inelastic Scattering (DIS) events using the ZEUS detector over a large range of Q(2) from 10 to 1280 GeV2 The evolution with Q of the charged multiplicity and scaled momentum has been investigated in the current fragmentation region of the Breit frame. The data are used to study QCD coherence effects in DIS and are compared with corresponding e(+)e(-) data in order to test the universality of quark fragmentation

JET PRODUCTION IN HIGH Q(2) DEEP-INELASTIC EP SCATTERING AT HERA RID B-9165-2008 RID C-5889-2009 RID A-4818-2008 RID C-1693-2008

Two-jet production in deep-inelastic electron-proton scattering has been studied for 160 < Q(2) < 1280 GeV2 0.01 < x < 0.1 and 0.04 < y < 0.95 with the ZEUS detector at HERA. The kinematic properties of the jets and the jet production rates are presented. The partonic scaling variables of the two-jet system and the rate of two-jet production are compared to perturbative next-to-leading order QCD calculations

MEASUREMENT OF TOTAL AND PARTIAL PHOTON PROTON CROSS-SECTIONS AT 180 GEV CENTER-OF-MASS ENERGY RID C-1693-2008 RID B-9165-2008 RID C-5889-2009 RID A-4818-2008

Photon proton cross sections for elastic light vector meson production, sigma(el)gammap, inelastic diffractive production, sigma(d)gammap, non-diffractive production, sigma(nd)gammap, as well as the total cross section, sigma(tot)gammap, have been measured at an average gammap center of mass energy of 180 GeV with the ZEUS detector at HERA. The resulting values are sigma(el)gammap = 18 +/- 7 mub, sigma(d)gammap = 33 +/- 8 mub, sigma(nd)gammap = 91 +/- 11 mub, and sigma(tot)gammap = 143 +/- 17 mub, where the errors include statistical and systematic errors added in quadrature