An Elicitation of the Dynamic Nature of Water Vapor Feedback in Climate Change Using a 1D Model

Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour is also the dominant greenhouse gas and contributes to a warming of the climate system by some 24°C (Kondratev 1972). However, water vapour is a passive component in the troposphere as it is uniquely determined by temperature and should therefore be seen as a part of the climate feedback system. In this short overview, we will first describe the water on planet Earth and the role of the hydrological cycle: the way water vapour is transported between oceans and continents and the return of water via rivers to the oceans. Generally water vapour is well observed and analysed; however, there are considerable obstacles to observing precipitation, in particular over the oceans. The response of the hydrological cycle to global warming is far reaching. Because different physical processes control the change in water vapour and evaporation/precipitation, this leads to a more extreme distribution of precipitation making, in general, wet areas wetter and dry areas dryer. Another consequence is a transition towards more intense precipitation. It is to be expected that the changes in the hydrological cycle as a consequence of climate warming may be more severe that the temperature changes.

Interactions involving various time and space scales, both within the tropics and between the tropics and midlatitudes, are ubiquitous in the climate system. We propose a conceptual framework for understanding such interactions whereby longer time scales and larger space scales set the base state for processes on shorter time scales and smaller space scales, which in turn have an influence back on the longer time scales and larger space scales in a continuum of process-related interactions. Though not intended to be comprehensive, we do cite examples from the literature to provide evidence for the validity of this framework. Decadal time scale base states of the coupled climate system set the context for the manifestation of interannual time scales (El Nino/Southern Oscillation, ENSO and tropospheric biennial oscillation, TBO) which are influenced by and interact with the annual cycle and seasonal time scales. Those base states in turn influence the large-scale coupled processes involved with intraseasonal and submonthly time scales, tied to interactions within the tropics and extratropics, and tropical–midlatitude teleconnections. All of these set the base state for processes on the synoptic and mesoscale and regional/local space scales. Events at those relatively short time scales and small space scales may then affect the longer time scale and larger space scale processes in turn, reaching back out to submonthly, intraseasonal, seasonal, annual, TBO, ENSO and decadal. Global coupled models can capture some elements of the decadal, ENSO, TBO, annual and seasonal time scales with the associated global space scales. However, coupled models are less successful at simulating phenomena at subseasonal and shorter time scales with hemispheric and smaller space scales. In the context of the proposed conceptual framework, the synergistic interactions of the time and space scales suggest that a high priority must be placed on improved simulations of all of the time and space scales in the climate system. This is particularly important for the subseasonal time scales and hemispheric and smaller space scales, which are not well simulated at present, to improve the prospects of successfully forecasting phenomena beyond the synoptic scales.

Heart rate variability (HRV) has been extensively explored by traditional linear approaches (e.g., spectral analysis); however, several studies have pointed to the presence of nonlinear features in HRV, suggesting that linear tools might fail to account for the complexity of the HRV dynamics. Even though the prevalent notion is that HRV is nonlinear, the actual presence of nonlinear features is rarely verified. In this study, the presence of nonlinear dynamics was checked as a function of time scales in three experimental models of rats with different impairment of the cardiac control: namely, rats with heart failure (HF), spontaneously hypertensive rats (SHRs), and sinoaortic denervated (SAD) rats. Multiscale entropy (MSE) and refined MSE (RMSE) were chosen as the discriminating statistic for the surrogate test utilized to detect nonlinearity. Nonlinear dynamics is less present in HF animals at both short and long time scales compared with controls. A similar finding was found in SHR only at short time scales. SAD increased the presence of nonlinear dynamics exclusively at short time scales. Those findings suggest that a working baroreflex contributes to linearize HRV and to reduce the likelihood to observe nonlinear components of the cardiac control at short time scales. In addition, an increased sympathetic modulation seems to be a source of nonlinear dynamics at long time scales. Testing nonlinear dynamics as a function of the time scales can provide a characterization of the cardiac control complementary to more traditional markers in time, frequency, and information domains.NEW & NOTEWORTHY Although heart rate variability (HRV) dynamics is widely assumed to be nonlinear, nonlinearity tests are rarely used to check this hypothesis. By adopting multiscale entropy (MSE) and refined MSE (RMSE) as the discriminating statistic for the nonlinearity test, we show that nonlinear dynamics varies with time scale and the type of cardiac dysfunction. Moreover, as complexity metrics and nonlinearities provide complementary information, we strongly recommend using the test for nonlinearity as an additional index to characterize HRV.

A method of calculating the past states of the earth‐moon system is developed. The method is based on the existence of three distinct time scales for dynamical change. The short time scale is determined by the revolution periods of the sun and moon about the earth or, equivalently, by the year and current month. The intermediate time scale is set by the precessional motions of the lunar orbit plane and the earth's equator plane. The rate at which tidal friction alters the state of the earth‐moon system defines the long time scale. The equations of motion governing the earth‐moon system are successively averaged over the short and then the intermediate time scales. These averaged equations are then integrated back a short interval on the long time scale. The equations of motion appropriate to this new state of the earth‐moon system are then re‐averaged on the short and intermediate time scales, and once again the averaged eqations are stepped back on the tidal time scale. The first step in this procedure (i.e. averaging on the short time scale) is performed analytically, whereas the calculations on the intermediate and long time scales require the use of a large computer.At present, the inclination of the lunar orbit plane to the ecliptic remains nearly constant during the precessional motion. On the other hand, if the moon's semimajor axis were ever less than 10R⨁, the inclination of the lunar orbit plane would have maintained a fixed value with respect to the earth's equator plane. The current investigation shows that this inclination could never have been less than 10° and, therefore, that the moon could never have moved on an equatorial orbit. This result contradicts theories that postulate fission of the earth to form the moon and also those which propose that the moon formed by accretion within 10R⨁

We present the characteristics of the X-ray variability of stars in the cluster NGC2516 as derived from XMM-Newton/EPIC/pn data. The X-ray variations on short (hours), medium (months), and long (years) time scales have been explored. We detected 303 distinct X-ray sources by analysing six EPIC/pn observations; 194 of them are members of the cluster. Stars of all spectral types, from the early-types to the late-M dwarfs, were detected. The Kolmogorov-Smirnov test applied to the X-ray photon time series shows that, on short time scales, only a relatively small fraction (ranging from 6% to 31% for dG and dF, respectively) of the members of NGC2516 are variable with a confidence level $\geq$99%; however, it is possible that the fraction is small only because of the poor statistics. The time X-ray amplitude distribution functions (XAD) of a set of dF7-dK2 stars, derived on short (hours) and medium (months) time scales, seem to suggest that medium-term variations, if present, have a much smaller amplitude than those on short time scales; a similar result is also obtained for dK3-dM stars. The amplitude variations of late-type stars in NGC2516 are consistent with those of the coeval Pleiades stars. Comparing these data with those of ROSAT/PSPC, collected 7-8 years earlier, and of ROSAT/HRI, just 4-5 years earlier, we find no evidence of significant variability on the related time scales, suggesting that long-term variations due to activity cycles similar to the solar cycle are not common among young stars. Indications of spectral variability was found in one star whose spectra at three epochs were available.

Water is a central component in the Earth’s system. It is indispensable for life on Earth in its present form and influences virtually every aspect of our planet’s life support system. On relatively short time scales, atmospheric water vapor interacts with the atmospheric circulation and is crucial in forming the Earth’s climate zones that determine where habitable areas can exist. On the longest time scales of hundreds of millions of years, water contributes to the lubrication of the movements of the tectonic plates, creating a pattern of change that has shaped and is continuing to shape the Earth. In the atmosphere, water vapor plays a key role in the Earth’s energy balance and regulates the Earth’s climate in a significant way. Water vapor is the most powerful of the greenhouse gases and serves to enhance the tropospheric temperature because water vapor is physically and dynamically controlled by atmospheric temperature and atmospheric circulation. The total amount of available water on the Earth amounts to some 1.5 9 10 9 km 3 . The dominant part of this, 1.4 9 10 9 km 3 , resides in the oceans. About 29 9 10 6 km 3 are locked up in the land ice on Greenland and Antarctica, and some 15 9 10 6 km 3 are estimated to exist as groundwater. If all the ice over the land and all the glaciers were to melt, as has happened several times in the Earth’s history, the sea level would rise by some 80 m. In comparison, the total amount of water vapor in the atmosphere is small; it amounts to *2.5 kg/m 2 , or the equivalent of 25 mm water for each column of air. Yet atmospheric water vapor is crucial for the Earth’s energy balance. The annual mean global values of evaporation and precipitation are *1,000 mm of water/m 2 . However, these values vary enormously in space and time from areas that are almost completely dry to areas where the annual precipitation is more than an order of magnitude larger than the global mean value. An evaporation of 1,000 mm of water/year corresponds to 80 W/m 2 in energy loss for the surface and a corresponding gain for the atmosphere when condensation takes place. This is the single largest component for heating the atmosphere; it is even larger than the direct solar energy absorbed by the

The 20-year (1976–1995) daily radiosonde data at 17 stations in the tropical western Pacific was analyzed. The analysis shows that the atmosphere is more humid in a warmer climate on seasonal, inter-annual and long-term (20-year) time scales, implying a positive water vapor feedback. The vertical structure of the long-term trends in relative humidity (RH) is distinct from that on short-term (seasonal and inter-annual) time scales, suggesting that observed water vapor changes on short time scales could not be considered as a surrogate of long-term climate change. The increasing trend of RH (3%–5% / decade) in the upper troposphere is stronger than that in the lower troposphere (1%2%–2% / decade). Such vertical structure would amplify positive water vapor feedback in comparison to the common assumption of constant RH changes vertically. The empirical orthogonal function (EOF) analysis of vertical structure of RH variations shows distinct features of the vertical structure of the first three EOFs. The first three EOFs are optimal for representation of water vapor profiles and provide some hints on physical mechanisms responsible for observed humidity variability. Vaisala radiosondes were used at nine stations, and VIZ radiosondes used at other eight stations. The Vaisala data are corrected for temperature-dependence error using the correction scheme developed by NCAR I A TD and Vaisala. The comparison of Vaisala and VIZ data shows that the VIZ-measured RHs after October 1993 have a moist bias of ~ 10% at RHs < 20%. During 1976–1995, several changes including both instruments and reporting practice have been made at Vaisala stations and introduce errors to long-term RH variations.

The time variation of Northern Hemisphere wintertime 500 mb height fluctuations with short, intermediate and long time scales is investigated, using lag-correlation patterns derived from time-filtered data. Fluctuations with short (2.5–6 day periods) time scales propagate eastward at a rate consistent with the notion of a steering level around 700 mb, which supports an interpretation in terms of baroclinic waves. The mobile teleconnection patterns associated with the intermediate (10–30 day periods) time scales exhibit a pattern of time variation suggestive a Rossby-wave dispersion, with a predominance of southward dispersion from middle latitudes into the tropics. The geographically fixed teleconnection patterns characteristic of the longer time scales do not show a well-defined pattern of time variation, but their horizontal structure resembles that of the fastest growing normal mode associated with barotropic instability of the climatological mean wintertime flow.

We developed a model with no adjustable parameter for retention loss at short and long time scales in ferroelectric thin-film capacitors. We found that the predictions of this model are in good agreement with the experimental observations in the literature. In particular, it explains why a power-law function shows better fitting than a linear-log relation on a short time scale (10−7 s to 1 s) and why a stretched exponential relation gives more precise description than a linear-log plot on a long time scale (&amp;gt;100 s), as reported by many researchers in the past. More severe retention losses at higher temperatures and in thinner films have also been correctly predicted by the present theory.

This study describes a new coupled ocean-atmosphere general circulation model (OAGCM) developed for studies of climate change and results from a hindcast experiment. The model includes various physical and technical improvements relative to an earlier version of the Hadley Centre OAGCM. A coupled spinup process is used to bring the model to equilibrium. Compared to uncoupled spinup methods this is computationally more expensive, but helps to counter climate drift arising from inadequate sampling of short time scale coupled variability when the components are equilibrated separately. Including sea ice advection and enhancing reference surface salinities in high southern latitudes in austral winter to promote bottom water formation during spinup appears to have stabilized the high-latitude drift exhibited in the earlier model’s control run. In the present study, the atmospheric control climate is stable on multi-century time scales with a drift in global average surface air temperature of only +0.016 K/century, despite a small residual drift in the deep ocean. The control climate is an improvement over the earlier model in several respects, notably in its variability on short time scales. Two anomaly runs are presented incorporating estimated forcing changes over the period 1860 to 1990 arising from greenhouse gases alone and from greenhouse gases plus the radiative scattering effect of sulphate aerosols. These allow validation of the model against the instrumental climate record. Inclusion of aerosol forcing gives a significantly better simulation of historical temperature patterns, although comparisons against recent sea ice trends are equivocal. These studies emphasize the potential importance of including additional forcing terms apart from greenhouse gases in climate simulations, and refining estimates of their spatial distribution and magnitude.

Sources of intermodel differences in the global lapse rate (LR) and water vapor (WV) feedbacks are assessed using CO2 forcing simulations from 28 general circulation models. Tropical surface warming leads to significant warming and moistening in the tropical and extratropical upper troposphere, signifying a nonlocal, tropical influence on extratropical radiation and feedbacks. Model spread in the locally defined LR and WV feedbacks is pronounced in the Southern Ocean because of large-scale ocean upwelling, which reduces surface warming and decouples the surface from the tropospheric response. The magnitude of local extratropical feedbacks across models and over time is well characterized using the ratio of tropical to extratropical surface warming. It is shown that model differences in locally defined LR and WV feedbacks, particularly over the southern extratropics, drive model variability in the global feedbacks. The cross-model correlation between the global LR and WV feedbacks therefore does not arise from their covariation in the tropics, but rather from the pattern of warming exerting a common control on extratropical feedback responses. Because local feedbacks over the Southern Hemisphere are an important contributor to the global feedback, the partitioning of surface warming between the tropics and the southern extratropics is a key determinant of the spread in the global LR and WV feedbacks. It is also shown that model Antarctic sea ice climatology influences sea ice area changes and southern extratropical surface warming. As a result, model discrepancies in climatological Antarctic sea ice area have a significant impact on the intermodel spread of the global LR and WV feedbacks.

Has China achieved synergistic reduction of carbon emissions and air pollution? Evidence from 283 Chinese cities

The nonlinear dynamics of biochemical reactions in a small-sized system on the order of a cell are stochastic. Assuming spatial homogeneity, the populations of n molecular species follow a multi-dimensional birth-and-death process on . We introduce the Delbrück–Gillespie process, a continuous-time Markov jump process, whose Kolmogorov forward equation has been known as the chemical master equation, and whose stochastic trajectories can be computed via the Gillespie algorithm. Using simple models, we illustrate that a system of nonlinear ordinary differential equations on emerges in the infinite system size limit. For finite system size, transitions among multiple attractors of the nonlinear dynamical system are rare events with exponentially long transit times. There is a separation of time scales between the deterministic ODEs and the stochastic Markov jumps between attractors. No diffusion process can provide a global representation that is accurate on both short and long time scales for the nonlinear, stochastic population dynamics. On the short time scale and near deterministic stable fixed points, Ornstein–Uhlenbeck Gaussian processes give linear stochastic dynamics that exhibit time-irreversible circular motion for open, driven chemical systems. Extending this individual stochastic behaviour-based nonlinear population theory of molecular species to other biological systems is discussed.

Using two versions of the GFDL coupled ocean‐atmosphere model, one where water vapor anomalies are allowed to affect the longwave radiation calculation and one where they are not, we examine the role of water vapor feedback in internal precipitation variability and greenhouse‐gas‐forced intensification of the hydrologic cycle. Without external forcing, the experiment with water vapor feedback produces 44% more annual‐mean, global‐mean precipitation variability than the one without. We diagnose the reason for this difference: In both experiments, global‐mean surface temperature anomalies are associated with water vapor anomalies. However, when water vapor interacts with longwave radiation, the temperature anomalies are associated with larger anomalies in surface downward longwave radiation. This increases the temperature anomaly damping through latent heat flux, creating an evaporation anomaly. The evaporation anomaly, in turn, leads to an anomaly of nearly the same magnitude in precipitation. In the experiment without water vapor feedback, this mechanism is absent. While the interaction between longwave and water vapor has a large impact on the global hydrologic cycle internal variations, its effect decreases as spatial scales decrease, so water vapor feedback has only a very small impact on grid‐scale hydrologic variability. Water vapor feedback also affects the hydrologic cycle intensification when greenhouse gas concentrations increase. By the 5th century of global warming experiments where CO2 is increased and then fixed at its doubled value, the global‐mean precipitation increase is nearly an order of magnitude larger when water vapor feedback is present. The cause of this difference is similar to the cause of the difference in internal precipitation variability: When water vapor feedback is present, the increase in water vapor associated with a warmer climate enhances downward longwave radiation. To maintain surface heat balance, evaporation increases, leading to a similar increase in precipitation. This effect is absent in the experiment without water vapor feedback. The large impact of water vapor feedback on hydrologic cycle intensification does not weaken as spatial scales decrease, unlike the internal variability case. Accurate representations of water vapor feedback are therefore necessary to simulate global‐scale hydrologic variability and intensification of the hydrologic cycle in global warming.

We present a comprehensive analysis of X-ray variability of the late-type (dF7-dM) Pleiades stars, detected in all ROSAT-PSPC observations; X-ray variations on short (hours) and medium (months) time scales have been explored. We have grouped the stars in two samples: 89 observations of 42 distinct dF7-dK2 stars and 108 observations of 61 dK3-dM stars. The Kolmogorov-Smirnov test applied on all X-ray photon time series show that the percentage of cases of significant variability is quite similar on both samples, suggesting that the presence of variability does not depend on mass for the time scales and mass range explored. The comparison between the Time X-ray Amplitude Distribution functions (XAD) of the set of dF7-dK2 and of the dK3-dM show that, on short time scales, dK3-dM stars show larger variations than dF7-dK2. A subsample of eleven dF7-dK2 and eleven dK3-dM Pleiades stars allows the study of variability on longer time scales: we found that variability on medium – long time scales is relatively more common among dF7-dK2 stars than among dK3-dM ones. For both dF7-dK2 Pleiades stars and dF7-dK2 field stars, the variability on short time scales depends on Lx while this dependence has not been observed among dK3-dM stars. It may be that the variability among dK3-dM stars is dominated by flares that have a similar luminosity distribution for stars of different Lx, while flaring distribution in dF7-dK2 stars may depend on X-ray luminosity. The lowest mass stars show significant rapid variability (flares?) and no evidence of rotation modulation or cycles. On the contrary, dF7-dK2 Pleiades stars show both rapid variability and variations on longer time scales, likely associated with rotational modulation or cycles.