scholarly journals Scaling of Precipitation Extremes over a Wide Range of Climates Simulated with an Idealized GCM

2009 ◽  
Vol 22 (21) ◽  
pp. 5676-5685 ◽  
Author(s):  
Paul A. O’Gorman ◽  
Tapio Schneider
Keyword(s):  
Precipitation Extremes ◽  
Lapse Rate ◽  
Fractional Rate ◽  
Rate Of Increase ◽  
Wide Range ◽  
Simple Scaling ◽  
Precipitation Increase ◽  
The Mean ◽  
The Difference ◽  
Global Mean

Abstract Extremes of precipitation are examined in a wide range of climates simulated with an idealized aquaplanet GCM. The high percentiles of daily precipitation increase as the climate warms. Their fractional rate of increase with global-mean surface temperature is generally similar to or greater than that of mean precipitation, but it is less than that of atmospheric (column) water vapor content. A simple scaling is introduced for precipitation extremes that accounts for their behavior by including the effects of changes in the moist-adiabatic lapse rate, the circulation strength, and the temperature when the extreme events occur. The effects of changes in the moist-adiabatic lapse rate and circulation strength on precipitation extremes are important globally, whereas the difference in the mean temperature and the temperature at which precipitation extremes occur is important only at middle to high latitudes.

The Atmospheric Energy Constraint on Global-Mean Precipitation Change

2014 ◽  
Vol 27 (2) ◽  
pp. 757-768 ◽  
Author(s):  
Angeline G. Pendergrass ◽  
Dennis L. Hartmann
Keyword(s):  
Water Vapor ◽  
Temperature Increase ◽  
Longwave Radiation ◽  
Surface Fluxes ◽  
Lapse Rate ◽  
Specific Humidity ◽  
Radiative Cooling ◽  
Rate Of Increase ◽  
Precipitation Increase ◽  
Global Mean

Abstract Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) robustly predict that the rate of increase in global-mean precipitation with global-mean surface temperature increase is much less than the rate of increase of water vapor. The goal of this paper is to explain in detail the mechanisms by which precipitation increase is constrained by radiative cooling. Changes in clear-sky atmospheric radiative cooling resulting from changes in temperature and humidity in global warming simulations are in good agreement with the multimodel, global-mean precipitation increase projected by GCMs (~1.1 W m−2 K−1). In an atmosphere with fixed specific humidity, radiative cooling from the top of the atmosphere (TOA) increases in response to a uniform temperature increase of the surface and atmosphere, while atmospheric cooling by exchange with the surface decreases because the upward emission of longwave radiation from the surface increases more than the downward longwave radiation from the atmosphere. When a fixed relative humidity (RH) assumption is made, however, uniform warming causes a much smaller increase of cooling at the TOA, and the surface contribution reverses to an increase in net cooling rate due to increased downward emission from water vapor. Sensitivity of precipitation changes to lapse rate changes is modest when RH is fixed. Carbon dioxide reduces TOA emission with only weak effects on surface fluxes, and thus suppresses precipitation. The net atmospheric cooling response and thereby the precipitation response to CO2-induced warming at fixed RH are mostly contributed by changes in surface fluxes. The role of clouds is discussed. Intermodel spread in the rate of precipitation increase across the CMIP5 simulations is attributed to differences in the atmospheric cooling.

scholarly journals Biology and life-table of Typhlodromus (Anthoseius) athenas (Acari: Phytoseiidae) fed with the Old World Date Mite, Oligonychus afrasiaticus (Acari: Tetranychidae)

Acarologia ◽  
2018 ◽  
Vol 58 (1) ◽  
pp. 52-61
Author(s):  
Samah Ben Chaaban ◽  
Brahim Chermiti ◽  
Serge Kreiter
Keyword(s):  
Life Table ◽  
Intrinsic Rate ◽  
Phoenix Dactylifera ◽  
Reproductive Rate ◽  
Intrinsic Rate Of Increase ◽  
Net Reproductive Rate ◽  
Old World ◽  
Rate Of Increase ◽  
Wide Range ◽  
The Mean

The old world date mite Oligonychus afrasiaticus is an important spider mite pest of the date palms Phoenix dactylifera L. mostly in North Africa and the Middle East. A population of the predaceous mite Typhlodromus (Anthoseius) athenas has been recently found in Tunisia in association with a decrease of O. afrasiaticus densities. The objective of this paper was to assess the development and reproduction abilities of T. ( A.) athenas on O. afrasiaticus under laboratory conditions at two temperatures: 27 and 32 °C. The results obtained show that females of T. (A.) athenas develop in 5 days at 27 °C and 4.1 days at 32 °C. The mean fecundity of T. (A.) athenas was 32.1 and 23.2 eggs per female at 27 and 32 °C, respectively. Life table parameters were stimated: the net reproductive rate (Ro) 27.9 and 17.9 eggs/female, the intrinsic rate of increase (rm) 0.322 and 0,344 female/female/day and the mean generation time (T) 10.3 and 8.4 days at 27 and 32 °C, respectively. At both temperatures tested, T. (A.) athenas intrinsic rate of increase was greater than that of O. afrasiaticus (rm = 0.213 at 32 °C,against rm = 0.166 day1 at 27 °C). Typhlodromus (A.) athenas would be able to develop at a wide range of temperatures feeding on O. afrasiaticus and seems to be able to potentially control it.

scholarly journals Impact of Convective Organization on the Response of Tropical Precipitation Extremes to Warming

2013 ◽  
Vol 26 (14) ◽  
pp. 5028-5043 ◽  
Author(s):  
Caroline Muller
Keyword(s):  
Water Vapor ◽  
Surface Water ◽  
Precipitation Extremes ◽  
Vertical Shear ◽  
Tropical Precipitation ◽  
Fractional Rate ◽  
Squall Lines ◽  
Rate Of Increase ◽  
Cloud Resolving Model ◽  
Organized Convection

Abstract In this study the response of tropical precipitation extremes to warming in organized convection is examined using a cloud-resolving model. Vertical shear is imposed to organize the convection into squall lines. Earlier studies show that in disorganized convection, the fractional increase of precipitation extremes is similar to that of surface water vapor, which is substantially smaller than the increase in column water vapor. It has been suggested that organized convection could lead to stronger amplifications. Regardless of the strength of the shear, amplifications of precipitation extremes in the cloud-resolving simulations are comparable to those of surface water vapor and are substantially less than increases in column water vapor. The results without shear and with critical shear, for which the squall lines are perpendicular to the shear, are surprisingly similar with a fractional rate of increase of precipitation extremes slightly smaller than that of surface water vapor. Interestingly, the dependence on shear is nonmonotonic, and stronger supercritical shear yields larger rates, close to or slightly larger than surface humidity. A scaling is used to evaluate the thermodynamic and dynamic contributions to precipitation extreme changes. To first order, they are dominated by the thermodynamic component, which has the same magnitude for all shears, close to the change in surface water vapor. The dynamic contribution plays a secondary role and tends to weaken extremes without shear and with critical shear, while it strengthens extremes with supercritical shear. These different dynamic contributions for different shears are due to different responses of convective mass fluxes in individual updrafts to warming.

scholarly journals Response Variability in Balanced Cortical Networks

2006 ◽  
Vol 18 (3) ◽  
pp. 634-659 ◽  
Author(s):  
Alexander Lerchner ◽  
Cristina Ursta ◽  
John Hertz ◽  
Mandana Ahmadi ◽  
Pauline Ruffiot ◽  
...  
Keyword(s):  
Mean Field ◽  
Excitatory Input ◽  
Response Variability ◽  
Cortical Column ◽  
Single Model ◽  
Wide Range ◽  
High Connectivity ◽  
The Mean ◽  
The Difference ◽  
External Population

We study the spike statistics of neurons in a network with dynamically balanced excitation and inhibition. Our model, intended to represent a generic cortical column, comprises randomly connected excitatory and inhibitory leaky integrate-and-fire neurons, driven by excitatory input from an external population. The high connectivity permits a mean field description in which synaptic currents can be treated as gaussian noise, the mean and autocorrelation function of which are calculated self-consistently from the firing statistics of single model neurons. Within this description, a wide range of Fano factors is possible. We find that the irregularity of spike trains is controlled mainly by the strength of the synapses relative to the difference between the firing threshold and the postfiring reset level of the membrane potential. For moderately strong synapses, we find spike statistics very similar to those observed in primary visual cortex.

A new approach to the measurement of the quantitative effects of inherent and environmental factors on the composition of the milk of individual cows and of herds, with particular reference to lactose content

1968 ◽  
Vol 35 (1) ◽  
pp. 91-105 ◽  
Author(s):  
J. P. Walsh ◽  
J. A. F. Rook ◽  
F. H. Dodd
Keyword(s):  
Quantitative Estimation ◽  
Relative Importance ◽  
New Approach ◽  
Mean Values ◽  
Stage Of Lactation ◽  
Bulk Milk ◽  
Wide Range ◽  
The Mean ◽  
The Difference ◽  
Effect Of Age

Summary(1) A tentative scheme is proposed for the quantitative estimation of the effects of various factors on one major milk constituent, lactose, from analyses of the milk of individual cows within herds. The potential lactose content in the milk of individual cows is predicted from the observed potassium-to-lactose ratio in the milk, and the difference between the predicted potential and the actual lactose content is partitioned into fractions that are attributed to effects due to age, inter-quarter difference and changes with stage of lactation. The scheme was applied to 2 commercial herds, one (herd A) producing milk of low and the other (herd B) milk of normal SNF content.(2) Lactation mean values for fat, SNF and lactose contents of the milk of individual cows showed a wide range of the same order in each of the 2 herds. Of the mean difference in SNF percentage of 0·30 between the herds, 0·14, or 47%, was due to a difference in lactose content.(3) The predicted potential milk lactose content of the cows in the 2 herds ranged from 5·04 to 5·66 (g/100 g milk water). Herd mean values were 5·394 for herd A and 5·244 for herd B.(4) Herd mean values for the effect on the lactose content (g/100 g milk water) of age, of changes with stage of lactation and of inter-quarter difference were −0·127, −0·080, and 0·073 respectively in herd A, and −0·197, −0·058 and −0·078, respectively, in herd B.(5) The relative importance of the various factors in accounting for differences between the herds in the lactose content of their bulk milk were: predicted potential lactose content 61%, effect of age 28%, effect of changes with stage of lactation 9% and effect of inter-quarter difference 2%.(6) The errors attached to the estimation of potential milk lactose content and the effects of age, of changes with stage of lactation and of inter-quarter difference are discussed.

scholarly journals Experimental and numerical investigation of the sintering rate of snow

2013 ◽  
Vol 59 (214) ◽  
pp. 269-274 ◽  
Author(s):  
Alec Van Herwijnen ◽  
Daniel A. Miller
Keyword(s):  
Numerical Investigation ◽  
Power Law ◽  
Penetration Resistance ◽  
The Other ◽  
Snow Sample ◽  
Rate Of Increase ◽  
Wide Range ◽  
Snow Metamorphism ◽  
The Mean ◽  
Snow Samples

AbstractSintering rates in snow were investigated by measuring changes in penetration resistance with time and by using a numerical snow metamorphism model. Periodic Snow Micro Penetrometer (SMP) measurements were performed on uniform snow samples covering a wide range of densities. The mean penetration resistance of snow increased with time according to a power law with an average exponent of 0.18. Simulated changes in the bond-to-grain ratio for simplified spherical ice grains followed a power law with an average exponent of 0.18, showing that the mean penetration resistance, as measured with the SMP, closely relates to bond-to-grain ratio in snow. For lower-density snow samples, consisting mostly of dendritic snow morphologies, the measured increase in penetration resistance was lower. This is likely the result of two competing processes: (1) strengthening of the snow sample due to the creation and growth of bonds and (2) weakening of the snow sample due to the formation of unbonded small rounded particles at the expense of larger dendritic forms. On the other hand, the rate of increase in penetration resistance for snow samples consisting of closely packed depth hoar was similar to that of rounded grains.

Impact of mortality, possibly due to herpesvirus, on pilchard Sardinops sagax stocks along the south coast of Western Australia in 1998-99

2000 ◽  
Vol 51 (6) ◽  
pp. 601 ◽  
Author(s):  
D. J. Gaughan ◽  
R. W. Mitchell ◽  
S. J. Blight
Keyword(s):  
Western Australia ◽  
Total Mortality ◽  
Simulation Models ◽  
Mortality Rates ◽  
Sea Surface ◽  
Sea Floor ◽  
Wide Range ◽  
The Mean ◽  
The Difference ◽  
The Impact

During progression of a mass mortality of Australian pilchards in late 1998 and early 1999, quantities of dead pilchards on the sea-surface, sea-floor and along beaches were estimated in three regions along southern Western Australia (WA) by use of transects. Total mortality was estimated at 17 590, 11193 and 144.4 t for Esperance, Bremer Bay and Albany respectively. Mortality rates at Esperance and Bremer Bay were similar at 74.5% and 64.7% respectively, with a mean of 69.6%. In contrast, estimated mortality at Albany was only 2.4%. Although the difference in total mortality between regions is probably related to differences in stock size, as determined by simulation models, the much lower estimate for Albany is probably an artefact of an over-estimated pilchard biomass and not due to large differences in actual mortality rates. Variability in estimates of both pilchard biomass and quantities killed resulted in a wide range of estimated mortality rates, with lower estimates for Esperance and Bremer Bay of 28.0% and 22.9% respectively. This represents a significant decline in the breeding stock of WA pilchards. If the impact was closer to the mean (69.6%), then pilchard stocks in WA are severely depressed.

scholarly journals Advances and limitations of atmospheric boundary layer observations with GPS occultation over southeast Pacific Ocean

2012 ◽  
Vol 12 (2) ◽  
pp. 903-918 ◽  
Author(s):  
F. Xie ◽  
D. L. Wu ◽  
C. O. Ao ◽  
A. J. Mannucci ◽  
E. R. Kursinski
Keyword(s):  
Boundary Layer ◽  
Pacific Ocean ◽  
Atmospheric Boundary Layer ◽  
Temperature Inversion ◽  
Lower Percentage ◽  
Trade Wind ◽  
Sampling Errors ◽  
Wide Range ◽  
The Mean ◽  
The Difference

Abstract. The typical atmospheric boundary layer (ABL) over the southeast (SE) Pacific Ocean is featured with a strong temperature inversion and a sharp moisture gradient across the ABL top. The strong moisture and temperature gradients result in a sharp refractivity gradient that can be precisely detected by the Global Positioning System (GPS) radio occultation (RO) measurements. In this paper, the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) GPS RO soundings, radiosondes and the high-resolution ECMWF analysis over the SE Pacific are analyzed. COSMIC RO is able to detect a wide range of ABL height variations (1–2 km) as observed from the radiosondes. However, the ECMWF analysis systematically underestimates the ABL heights. The sharp refractivity gradient at the ABL top frequently exceeds the critical refraction (e.g., −157 N-unit km−1) and becomes the so-called ducting condition, which results in a systematic RO refractivity bias (or called N-bias) inside the ABL. Simulation study based on radiosonde profiles reveals the magnitudes of the N-biases are vertical resolution dependent. The $N$-bias is also the primary cause of the systematically smaller refractivity gradient (rarely exceeding −110 N-unit km−1) at the ABL top from RO measurement. However, the N-bias seems not affect the ABL height detection. Instead, the very large RO bending angle and the sharp refractivity gradient due to ducting allow reliable detection of the ABL height from GPS RO. The seasonal mean climatology of ABL heights derived from a nine-month composite of COSMIC RO soundings over the SE Pacific reveals significant differences from the ECMWF analysis. Both show an increase of ABL height from the shallow stratocumulus near the coast to a much higher trade wind inversion further off the coast. However, COSMIC RO shows an overall deeper ABL and reveals different locations of the minimum and maximum ABL heights as compared to the ECMWF analysis. At low latitudes, despite the decreasing number of COSMIC RO soundings and the lower percentage of soundings that penetrate into the lowest 500-m above the mean-sea-level, there are small sampling errors in the mean ABL height climatology. The difference of ABL height climatology between COSMIC RO and ECMWF analysis over SE Pacific is significant and requires further studies.

scholarly journals Advances and limitations of atmospheric boundary layer observations with GPS occultation over Southeast Pacific Ocean

2011 ◽  
Vol 11 (8) ◽  
pp. 22857-22891
Author(s):  
F. Xie ◽  
D. L. Wu ◽  
C. O. Ao ◽  
A. J. Mannucci ◽  
E. R. Kursinski
Keyword(s):  
Boundary Layer ◽  
Pacific Ocean ◽  
Atmospheric Boundary Layer ◽  
Temperature Inversion ◽  
Lower Percentage ◽  
Trade Wind ◽  
Sampling Errors ◽  
Wide Range ◽  
The Mean ◽  
The Difference

Abstract. The typical atmospheric boundary layer (ABL) over the southeast (SE) Pacific Ocean is featured with a strong temperature inversion and a sharp moisture gradient across the ABL top. The strong moisture and temperature gradients result in a sharp refractivity gradient that can be precisely detected by the Global Positioning System (GPS) radio occultation (RO) measurements. In this paper, the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS RO soundings, radiosondes and the high-resolution ECMWF analysis over the SE Pacific are analyzed. COSMIC RO is able to detect a wide range of ABL height variations (1–2 km) as observed from the radiosondes. Whereas, the ECMWF analyses systematically underestimate ABL heights. The sharp refractivity gradient at the ABL top frequently exceeds the critical refraction (e.g., −157 N-unit km−1) and becomes the so-called ducting condition, which results in systematic RO refractivity bias (or called N-bias) inside the ABL. Simulation study using refractivity profiles based on radiosondes reveals that the N-biases are significant and the magnitudes of biases are vertical resolution dependent. The N-bias is also the primary cause of the systematically smaller refractivity gradient (rarely exceeding −110 N-unit km−1) at the ABL top from RO measurement. However, the N-bias seems not affect the ABL height detection. Instead, the very sharp refractivity gradient and the large RO bending angle due to ducting allow reliable detection of ABL height from GPS RO. The seasonal mean climatology of ABL heights derived from a nine-month composite of COSMIC RO soundings over the SE Pacific reveals significant differences from the ECMWF analysis. Both show the deepening of ABL height from the shallow stratocumulus near the coast to a much higher trade wind inversion further off the coast. However, COSMIC RO shows systematically higher ABL heights overall and reveals different locations of the minimum and maximum ABL heights as compared to the ECMWF analysis. The significantly decreasing number of COSMIC RO soundings at lower latitudes along with the lower percentage of RO soundings penetrating into the lowest 500 m above mean-sea-level (a.m.s.l.), result in generally small sampling errors in the mean ABL climatology and will not affect the morphology of RO ABL height climatology. The difference of ABL height climatology between COSMIC RO and ECMWF analysis over SE Pacific is significant and requires further studies.

Assessing the vulnerability of organic matter to C mineralisation in pasture and cropping soils of New Zealand

Soil Research ◽  
2018 ◽  
Vol 56 (5) ◽  
pp. 481 ◽  
Author(s):  
Sam McNally ◽  
Mike Beare ◽  
Denis Curtin ◽  
Craig Tregurtha ◽  
Weiwen Qiu ◽  
...  
Keyword(s):  
New Zealand ◽  
Organic Carbon ◽  
Cold Water ◽  
Exponential Model ◽  
Hot Water ◽  
Environmental Perturbations ◽  
Wide Range ◽  
C Mineralisation ◽  
The Mean ◽  
The Difference

In New Zealand, pastoral soils have substantial organic carbon (OC) stocks, which may be vulnerable to loss from disturbance and environmental perturbations. We assessed OC vulnerability using two approaches. For the first approach, we postulated that the OC deficit of continuously cropped soils relative to nearby pastoral soils would provide a measure of the quantity of potentially vulnerable OC in pastures. As a test, soils were sampled to a depth of 15 cm at 149 sites and the total organic carbon (TOC) and particulate organic carbon (POC) contents were measured. The second approach involved measurement of OC mineralisation in a laboratory assay (98 day aerobic incubation at 25°C). For the pastoral soils, the mean TOC and POC was about twice that of the cropped soils. On average, 89% more OC was mineralised from the pastoral soils compared with the cropped counterparts. However, the quantity of OC mineralised in pasture soils was small relative to the potential for OC loss inferred from the difference in TOC between pastoral and cropped soils. Carbon mineralisation was explained using a two-pool exponential model with rate constants of the ‘fast’ and ‘slow’ pools equating to 0.36 ± 0.155 and 0.007 ± 0.003 day–1 respectively. The larger, slow OC pool correlated strongly with hot water extractable OC whereas the fast pool was related to OC extracted using cold water. Our results suggest that water extraction (using cold and hot water) can provide a rapid estimate of the quantity of mineralisable OC across a wide range of New Zealand soils.

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