Changes in future precipitation mean and variability across scales

Changes in precipitation variability can have large societal consequences, whether at the short timescales of flash floods or the longer timescales of multi-year droughts. Recent studies have suggested that in future climate projections, precipitation variability rises more steeply than does its mean, leading to concerns about societal impacts. This work evaluates changes in mean precipitation over a broad range of spatial and temporal scales using a range of models from high-resolution regional simulations to millennial-scale global simulations. Results show that changes depend on the scale of aggregation and involve strong regional differences. On local scales that resolve individual rainfall events (hours and tens of kilometers), changes in precipitation distributions are complex and variances rise substantially more than means, as is required given the well-known disproportionate rise in precipitation intensity. On scales that aggregate across many events, distributional changes become simpler and variability changes smaller. At regional scale, future precipitation distributions can be largely reproduced by a simple transformation of present-day precipitation involving a multiplicative shift and a small additive term. The “extra” broadening is negatively correlated with changes in mean precipitation: in strongly “wetting” areas, distributions broaden less than expected from a simple multiplicative mean change; in “drying” areas, distributions narrow less. Precipitation variability changes are therefore of especial concern in the subtropics, which tend to dry under climate change. Outside the tropics, variability changes are similar on timescales from days to decades, i.e. show little frequency dependence. This behavior is highly robust across models, suggesting it may stem from some fundamental constraint.

Establishment of AIRS climate-level radiometric stability using radiance anomaly retrievals of minor gases and sea surface temperature

Temperature, H2O, and O3 profiles, as well as CO2, N2O, CH4, chlorofluorocarbon-12 (CFC-12), and sea surface temperature (SST) scalar anomalies are computed using a clear subset of AIRS observations over ocean for the first 16 years of NASA's Earth-Observing Satellite (EOS) Aqua Atmospheric Infrared Sounder (AIRS) operation. The AIRS Level-1c radiances are averaged over 16 d and 40 equal-area zonal bins and then converted to brightness temperature anomalies. Geophysical anomalies are retrieved from the brightness temperature anomalies using a relatively standard optimal estimation approach. The CO2, N2O, CH4, and CFC-12 anomalies are derived by applying a vertically uniform multiplicative shift to each gas in order to obtain an estimate for the gas mixing ratio. The minor-gas anomalies are compared to the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) in situ values and used to estimate the radiometric stability of the AIRS radiances. Similarly, the retrieved SST anomalies are compared to the SST values used in the ERA-Interim reanalysis and to NOAA's Optimum Interpolation SST (OISST) product. These intercomparisons strongly suggest that many AIRS channels are stable to better than 0.02 to 0.03 K per decade, well below climate trend levels, indicating that the AIRS blackbody is not drifting. However, detailed examination of the anomaly retrieval residuals (observed – computed) shows various small unphysical shifts that correspond to AIRS hardware events (shutdowns, etc.). Some examples are given highlighting how the AIRS radiance stability could be improved, especially for channels sensitive to N2O and CH4. The AIRS shortwave channels exhibit larger drifts that make them unsuitable for climate trending, and they are avoided in this work. The AIRS Level 2 surface temperature retrievals only use shortwave channels. We summarize how these shortwave drifts impacts recently published comparisons of AIRS surface temperature trends to other surface climatologies.

Establishment of AIRS Climate-Level Radiometric Stability using Radiance Anomaly Retrievals of Minor Gases and SST

Temperature, H2O, and O3 profiles, as well as CO2, N2O, CH4, CFC12, and SST scalar anomalies are computed using a clear subset of AIRS observations over ocean for the first 16-years of NASA's EOS-AQUA AIRS operation. The AIRS Level 1c radiances are averaged over 16 days and 40 equal-area zonal bins and then converted to brightness temperature anomalies. Geophysical anomalies are retrieved from the brightness temperature anomalies using a relatively standard optimal estimation approach. The CO2, N2O, CH4, and CFC12 anomalies are derived by applying a vertically uniform multiplicative shift to each gas in order to obtain an estimate for the ngas mixing ratio. The minor gas anomalies are compared to the NOAA ESRL in-situ values and used to estimate the radiometric stability of the AIRS radiances. Similarly the retrieved SST anomalies are compared to the SST values used in the ERA-Interim reanalysis and to NOAA's OISST SST product. These inter-comparisons strongly suggest that many AIRS channels are stable to better than 0.02 to 0.03 K/Decade, well below climate trend levels, indicating that the AIRS blackbody is not drifting. However, detailed examination of the anomaly retrieval residuals (observed minus computed) show various small unphysical shifts that correspond to AIRS hardware events (shutdowns, etc.). Some examples are given highlighting how the AIRS radiances stability could be improved, especially for channels sensitive to N2O and CH4. The AIRS short wave channels exhibit larger drifts that make them unsuitable for climate trending, and they are avoided in this work. The AIRS Level 2 surface temperature retrievals only use short wave channels. We summarize how these short wave drifts impacts recently published comparisons of AIRS surface temperature trends to other surface climatologies.

The effect of scanning speed on texture-elicited vibrations

ABSTRACTTo sense the texture of a surface, we run our fingers across it, which leads to the elicitation of skin vibrations that depend both on the surface and on exploratory parameters, particularly scanning speed. The transduction and processing of these vibrations mediates the ability to discern fine surface features. In the present study, we seek to characterize the effect of changes in scanning speed on texture-elicited vibrations to better understand how the exploratory strategy shapes the neuronal representation of texture. To this end, we scanned a variety of textures across the fingertip of human participants at a variety of speeds (10 – 160 mm/s) while measuring the resulting vibrations using a laser Doppler vibrometer. We found that increases in speed led to systematic increases in vibratory intensity and to a systematic upward multiplicative shift in the frequency composition of the vibrations. Furthermore, we showed that the upward shift in frequency composition accounts for the increase in intensity. The enhancement of higher frequency components accounts for the observed increase in the firing rates of nerve fibers, particularly Pacinian corpuscle-associated fibers, which are most sensitive at the high frequencies.

Paired integral operators with homogeneous kernels perturbated by operators of multiplicative shift

В пространстве Lp(Rn), где 1⩽p⩽∞, рассматривается оператор B, представляющий собой сумму двух слагаемых. Первое слагаемое - это парный многомерный интегральный оператор, ядра которого однородны степени (−n) и инвариантны относительно группы вращений пространства Rn, а второе слагаемое - сходящийся по операторной норме ряд, составленный из многомерных операторов мультипликативного сдвига с комплексными коэффициентами. На ядра и коэффициенты оператора B накладываются некоторые дополнительные условия, обеспечивающие его ограниченность в пространстве суммируемых функций. Основная цель работы заключается в исследовании обратимости оператора B. Для решения этой задачи применяется специальный метод, позволяющий осуществить редукцию многомерного парного оператора к бесконечной последовательности одномерных парных операторов Bm, где m∈Z+. Показано, что оператор B обратим в том и только в том случае, когда обратимы все операторы Bm, где m пробегает все значения от нуля до некоторого конечного числа m0. В свою очередь, операторы Bm сводятся к интегрально-разностным операторам свертки, теория которых хорошо известна. Все это позволило для рассматриваемого оператора B определить символ, который представляет собой пару функций (β1(m,ξ),β2(m,ξ)), заданных на множестве Z+×R. Если символ является невырожденным, то естественным образом определяются вещественное число ν и целые числа ϰm, где m∈Z+, называемые индексами. Основной результат работы - критерий обратимости в пространстве Lp(Rn) многомерного парного оператора B. Согласно этому критерию, оператор B обратим тогда и только тогда, когда его символ является невырожденным, а все его индексы равны нулю.

On multidimensional integral operators with homogeneous kernels perturbated by one-sided multiplicative shift operators

Рассматриваются многомерные интегральные операторы, ядра которых однородны степени (−n) и инвариантны относительно группы вращений, возмущенные операторами одностороннего мультипликативного сдвига. Получены критерии обратимости и односторонней обратимости таких операторов в Lp-пространствах.

The Visual Callosal Connection: A Connection Like Any Other?

Recent work about the role of visual callosal connections in ferrets and cats is reviewed, and morphological and functional homologies between the lateral intrinsic and callosal network in early visual areas are discussed. Both networks selectively link distributed neuronal groups with similar response properties, and the actions exerted by callosal input reflect the functional topography of those networks. This supports the notion that callosal connections perpetuate the function of the lateral intrahemispheric circuit onto the other hemisphere. Reversible deactivation studies indicate that the main action of visual callosal input is a multiplicative shift of responses rather than a changing response selectivity. Both the gain of that action and its excitatory-inhibitory balance seem to be dynamically adapted to the feedforward drive by the visual stimulus onto primary visual cortex. Taken together anatomical and functional evidence from corticocortical and lateral circuits further leads to the conclusion that visual callosal connections share more features with lateral intrahemispheric connections on the same hierarchical level and less with feedback connections. I propose that experimental results about the callosal circuit in early visual areas can be interpreted with respect to lateral connectivity in general.

Measurements of ‘Von Kries’ Contrast Colours

At two previous ECVPs we showed demonstrations and preliminary measurements of contrast colours in a haploscopic display. Colours were presented in different uniform surrounds to the two eyes, superimposed in the binocular field so that they appeared to be in the same surround. Here we report more extensive matching experiments. The principal results are as follows: (1) To a first approximation, in a log MacLeod - Boynton space, perceived colour is determined by the surround-to-colour vector (SCV). The remaining results are second-order deviations from this von Kries scheme. (2) Increment colours are tinged with the hue of the surround, even though that surround hue cannot be seen. This effect of the sign of luminance contrast seems to be just a multiplicative shift: otherwise, increment and decrement data can be superimposed. (3) SCVs for a constant perceived colour shrink and expand slightly with movement along the S-cone axis, suggesting that the transform of S-cone excitation is less compressive than a logarithmic function. (4) SCVs show consistent small rotations, suggesting that L- M and S-( L+ M) axes are not completely independent.