scholarly journals Shallow-cloud impact on climate and uncertainty: A simple stochastic model

2020 ◽  
Vol 6 (1) ◽  
pp. 16-37
Author(s):  
Eli A. Mueller ◽  
Samuel N. Stechmann
Keyword(s):  
Climate Variability ◽  
Statistical Physics ◽  
Carbon Dioxide Concentration ◽  
Statistical Equilibrium ◽  
Cloud Formation ◽  
State Transitions ◽  
Intrinsic Variability ◽  
Sharp Transition ◽  
Shallow Clouds ◽  
The Mean

AbstractShallow clouds are a major source of uncertainty in climate predictions. Several different sources of the uncertainty are possible—e.g., from different models of shallow cloud behavior, which could produce differing predictions and ensemble spread within an ensemble of models, or from inherent, natural variability of shallow clouds. Here, the latter (inherent variability) is investigated, using a simple model of radiative statistical equilibrium, with oceanic and atmospheric boundary layer temperatures, To and Ta, and with moisture q and basic cloud processes. Stochastic variability is used to generate a statistical equilibrium with climate variability. The results show that the intrinsic variability of the climate is enhanced due to the presence of shallow clouds. In particular, the on-and-off switching of cloud formation and decay is a source of additional climate variability and uncertainty, beyond the variability of a cloud-free climate. Furthermore, a sharp transition in the mean climate occurs as environmental parameters are changed, and the sharp transition in the mean is also accompanied by a substantial enhancement of climate sensitivity and uncertainty. Two viewpoints of this behavior are described, based on bifurcations and phase transitions/statistical physics. The sharp regime transitions are associated with changes in several parameters, including cloud albedo and longwave absorptivity/carbon dioxide concentration, and the climate state transitions between a partially cloudy state and a state of full cloud cover like closed-cell stratocumulus clouds. Ideas of statistical physics can provide a conceptual perspective to link the climate state transitions, increased climate uncertainty, and other related behavior.

scholarly journals Responses of runoff to historical and future climate variability over China

2017 ◽  
Author(s):  
Chuanhao Wu ◽  
Bill X. Hu ◽  
Guoru Huang ◽  
Peng Wang ◽  
Kai Xu
Keyword(s):  
Climate Variability ◽  
Arid Regions ◽  
Southern China ◽  
Aridity Index ◽  
Global Climate Models ◽  
Future Climate ◽  
Western China ◽  
Climate Projections ◽  
Positive Contribution ◽  
The Mean

Abstract. China has suffered some of the effects of global warming, and one of the potential implications of climate warming is the alteration of the temporal-spatial patterns of water resources. Based on the long-term (1960–2012) water budget data and climate projections from 28 Global Climate Models (GCMs) of the Coupled Model Intercomparison Project Phase 5 (CMIP5), this study investigated the responses of runoff (R) to historical and future climate variability in China at both grid and catchment scales using the Budyko-based elasticity method. Results show that there is a large spatial variation in precipitation (P) elasticity (from 1.2 to 3.3) and potential evaporation (PET) elasticity (from −2.3 to −0.2) across China. The P elasticity is larger in northeast and western China than in southern China, while the opposite occurs for PET elasticity. The catchment properties elasticity of R appears to have a strong non-linear relationship with the mean annual aridity index and tends to be more significant in more arid regions. For the period 1960–2012, the climate contribution to R ranges from −2.4 % a−1 to 3.3 % a−1 across China, with the negative contribution in the North China plain and the positive contribution in western China and some parts of the southwest. The results of climate projections indicate that although there is large uncertainty involved in the 28 GCMs, most project a consistent change in P (or PET) in China at the annual scale. For the period 2071–2100, the mean annual P will likely increase in most parts of China, especially the western regions, while the mean annual PET will likely increase in all of China, particularly the southern regions. Furthermore, greater increases are projected for higher emission scenarios. Overall, due to climate change, the arid regions and humid regions of China will likely become wetter and drier in the period 2071–2100, respectively (relative to the baseline 1971–2000).

scholarly journals The Meridional Mode in an Idealized Aquaplanet Model: Dependence on the Mean State

2016 ◽  
Vol 29 (8) ◽  
pp. 2889-2905 ◽  
Author(s):  
Honghai Zhang ◽  
Amy Clement ◽  
Brian Medeiros
Keyword(s):  
Climate Variability ◽  
Coupled System ◽  
Ocean Model ◽  
Seasonal Migration ◽  
Trade Winds ◽  
Zonal Asymmetry ◽  
The Mean ◽  
Meridional Mode ◽  
Mean Climate ◽  
Mean State

Abstract The meridional mode provides a source of predictability for the tropical climate variability and change on seasonal and longer time scales by transporting extratropical climate signals into the tropics. Previous research shows that the tropical imprint of the meridional mode is constrained by the interhemispheric asymmetry of the tropical mean climate state. In this study the constraint of the zonal asymmetry is investigated in an AGCM thermodynamically coupled with an aquaplanet slab ocean model. The strategy is to modify the zonal asymmetry of the mean climate state and examine the response of the meridional mode. Presented here are two simulations of different zonal asymmetries in the mean state. In the zonally symmetric case, the meridional mode operates throughout the subtropics but only becomes evident after removing a dominant global-scale eastward-propagating mode. In the zonally asymmetric case, the meridional mode operates only in regions where trade winds converge onto the equator and has an enlarged spatial scale due to the modified mean climate including cold sea surface and weak trade winds. In both simulations, the tropical imprint of the meridional mode is constrained by the north–south seasonal migration of the intertropical convergence zone. These results suggest that the meridional mode does not require the zonal asymmetry of the mean state but is intrinsic to the subtropical ocean–atmosphere coupled system with its characteristics subject to the mean climate state. The implication is that the internal climate variability needs to be assessed in the context of the mean climate state.

FINITE-RANGE CONTACT PROCESS ON THE MARKET RETURN INTERVALS DISTRIBUTIONS

2010 ◽  
Vol 13 (05) ◽  
pp. 643-657 ◽  
Author(s):  
JUNHUAN ZHANG ◽  
JUN WANG ◽  
JIGUANG SHAO
Keyword(s):  
Stock Price ◽  
Statistical Physics ◽  
Scaling Function ◽  
Contact Process ◽  
Composite Index ◽  
Finite Range ◽  
Price Model ◽  
Simulation Data ◽  
The Mean ◽  
The Scaling Function

Stochastic system is applied to describe and investigate the fluctuations of stock price changes in a stock market, and a stock price model is developed by the finite-range contact process of the statistical physics systems. In this paper, the scaling behaviors of the return intervals for SSE Composite Index (SSE) and the simulation data of the model are investigated and compared. The database is from the index of SSE in the 6-year period for every 5 minutes, and the simulation data is from the finite-range contact model for different values of the range R. For different values of threshold θ, the statistical analysis shows that the probability density function Pθ(τ) of the return intervals τ for both SSE and the simulation data have similar scaling form, that is [Formula: see text] ([Formula: see text] is the mean return interval), where the scaling function h(x) can be approximately fitted by the function h(x) = ωe-a(ln x)γ, and ω, a, γ are three parameters. Further, with different values of R and θ, the statistical comparison of SSE Composite Index and simulation data are given.

scholarly journals Trend  Analysis of Climate variables, Stream flow and their Linkage at Modjo River Watershed, Central Ethiopia

2020 ◽  
Author(s):  
Kokeb Zena ◽  
Tamene Adugna ◽  
Fekadu Fufa
Keyword(s):  
Climate Variability ◽  
Trend Analysis ◽  
Stream Flow ◽  
Management Practices ◽  
River Flow ◽  
Pearson Correlation ◽  
Kendall Test ◽  
Precipitation Series ◽  
River Watershed ◽  
The Mean

Abstract Background: Trend and variability analysis of precipitation and stream flow series provides valuable information to understand hydrological changes associated with climate variability. In this study, annual and seasonal trends of precipitation and stream flow series and their relationship was investigated over the Modjo river watershed. The Mann-Kendall test and Sen’s slope estimator were used for trend analysis and evaluation of its magnitude respectively, with an approach that corrects the serial correlation. The Pearson correlation analysis was also applied to evaluate the relationships between river flow and precipitation series.Results: the mean and maximum stream flow series showed downward trends at the annual and kiremt time series, whereas no significant trend was observed for the minimum flow over the Modjo watershed. The study indicated that the mean annual and kiremt (monsoon) stream flow decreased significantly at a rate of 8.262 and 6.528 m3s-1per year respectively. In contrary to the river flow, there is no positive or negative trend in the annual and seasonal precipitation series although the tendency was towards increasing trends. It was evidenced that the annual, and kiremt season river flow series was affected abruptly since 2000, however for the same analysis period there was no evidence of changes in precipitation events, which is also not related significantly with the variability of river flow during the analysis period.Conclusions: the river flow decreased dramatically in the Modjo watershed during the analysis period (1981-2015), however it was not primarily associated significantly with climate variability (precipitation & temperature). The result suggests the need of considering the unplanned water extraction and the poor land use management practices to sustain and restore river flow trend observed in the watershed.

scholarly journals Aerosol-cirrus interactions: A number based phenomenon at all?

2003 ◽  
Vol 3 (4) ◽  
pp. 3625-3657
Author(s):  
M. Seifert ◽  
J. Ström ◽  
R. Krejci ◽  
A. Minikin ◽  
A. Petzold ◽  
...  
Keyword(s):  
Aerosol Particles ◽  
Cloud Formation ◽  
Data Sets ◽  
Number Density ◽  
Cloud Droplets ◽  
Data Set ◽  
Local Maxima ◽  
The Mean ◽  
Positive Correlations ◽  
Aerosol Cloud Interactions

Abstract. In situ measurements of the partitioning of aerosol particles within cirrus clouds were used to investigate aerosol-cloud interactions in ice clouds. The number density of interstitial aerosol particles (non-activated particles in between the cirrus crystals) was compared to the number density of cirrus crystal residuals. The data was obtained during the two INCA (Interhemispheric Differences in Cirrus Properties form Anthropogenic Emissions) campaigns, performed in the Southern Hemisphere (SH) and Northern Hemisphere (NH) midlatitudes. Different aerosol-cirrus interactions can be linked to the different stages of the cirrus lifecycle. Cloud formation is linked to positive correlations between the number density of interstitial aerosol (Nint) and crystal residuals (Ncvi), whereas the correlations are smaller or even negative in a dissolving cloud. Unlike warm clouds, where the number density of cloud droplets is positively related to the aerosol number density, we observed a rather complex relationship when expressing Ncvi as a function of Nint for forming clouds. The data sets are similar in that they both show local maxima in the Nint range 100 to 200 cm−3, where the SH-maximum is shifted towards the higher value. For lower number densities Nint and Ncvi are positively related. The slopes emerging from the data suggest that a tenfold increase in the aerosol number density corresponds to a 3 to 4 times increase in the crystal number density. As Nint increases beyond the ca. 100 to 200 cm−3, the mean crystal number density decreases at about the same rate for both data sets. For much higher aerosol number densities, only present in the NH data set, the mean Ncvi remains low. The situation for dissolving clouds presents two alternative interactions between aerosols and cirrus. Either evaporating clouds are associated with a source of aerosol particles, or air pollution (high aerosol number density) retards evaporation rates.

scholarly journals Ratio-based sensing of two transcription factors regulates the transit to differentiation

2018 ◽  
Author(s):  
Sebastian M. Bernasek ◽  
Jean-François Boisclair Lachance ◽  
Nicolás Peláez ◽  
Rachael Bakker ◽  
Heliodoro Tejedor Navarro ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Progenitor Cells ◽  
Cell Fate ◽  
Statistical Physics ◽  
Gene Dosage ◽  
State Transitions ◽  
Developmental Context ◽  
The Absolute

ABSTRACTCells must reliably respond to changes in transcription factor levels in order to execute cell state transitions in the correct time and place. These transitions are typically thought to be triggered by changes in the absolute nuclear concentrations of relevant transcription factors. We have identified a developmental context in which cell fate transitions depend on changes in the relative concentrations of two transcription factors. Here, we quantify the in vivo expression dynamics of Yan and Pointed, two essential E-twenty-six (ETS) proteins that regulate transcription during eye development in Drosophila. These two factors exert opposing influences; one impedes transcription of gene targets required for differentiation while the other promotes it. We show that both proteins are transiently co-expressed in eye progenitor cells and also during photoreceptor specification. To decide whether to undergo state transitions, cells respond to the ratio of the two protein concentrations rather than changes in the absolute abundance of either transcription factor. We show that a simple model based on the statistical physics of protein-DNA binding illustrates how this ratiometric sensing of transcription factor concentrations could occur. Gene dosage experiments reveal that progenitor cells stabilize the ratio against fluctuations in the absolute concentration of either protein. We further show that signaling inputs via the Notch and Receptor Tyrosine Kinase (RTK) pathways set the ratio in progenitor cells, priming them for either transit to differentiation or for continued multipotency. A sustained change in the ratio accompanies the transit to differentiation This novel mechanism allows for distributed control of developmental transitions by multiple transcription factors, making the system robust to fluctuating genetic or environmental conditions.

scholarly journals Probing the physical properties of the intergalactic medium using blazars

2021 ◽  
Vol 508 (2) ◽  
pp. 1701-1718
Author(s):  
Tony Dalton ◽  
Simon L Morris ◽  
Michele Fumagalli ◽  
Efrain Gatuzz
Keyword(s):  
Intergalactic Medium ◽  
Gamma Ray ◽  
Power Laws ◽  
Intrinsic Variability ◽  
Redshift Range ◽  
Exposure Data ◽  
Hydrogen Column Density ◽  
Source Data ◽  
The Mean ◽  
Collisional Ionization

ABSTRACT We use Swift blazar spectra to estimate the key intergalactic medium (IGM) properties of hydrogen column density ($\mathit {N}\small {\rm HXIGM}$), metallicity, and temperature over a redshift range of 0.03 ≤ z ≤ 4.7, using a collisional ionization equilibrium model for the ionized plasma. We adopted a conservative approach to the blazar continuum model given its intrinsic variability and use a range of power-law models. We subjected our results to a number of tests and found that the $\mathit {N}\small {\rm HXIGM}$ parameter was robust with respect to individual exposure data and co-added spectra for each source, and between Swift and XMM–Newton source data. We also found no relation between $\mathit {N}\small {\rm HXIGM}$ and variations in source flux or intrinsic power laws. Though some objects may have a bulk Comptonization component that could mimic absorption, it did not alter our overall results. The $\mathit {N}\small {\rm HXIGM}$ from the combined blazar sample scales as (1 + z)1.8 ± 0.2. The mean hydrogen density at z = 0 is n0 = (3.2 ± 0.5) × 10−7 cm−3. The mean IGM temperature over the full redshift range is log(T/K) =6.1 ± 0.1, and the mean metallicity is [X/H] = −1.62 ± 0.04(Z ∼ 0.02). When combining with the results with a gamma-ray burst (GRB) sample, we find the results are consistent over an extended redshift range of 0.03 ≤ z ≤ 6.3. Using our model for blazars and GRBs, we conclude that the IGM contributes substantially to the total absorption seen in both blazar and GRB spectra.

scholarly journals Statistical Structure of Intrinsic Climate Variability under Global Warming

2016 ◽  
Vol 29 (16) ◽  
pp. 5935-5947 ◽  
Author(s):  
Xiuhua Zhu ◽  
John Bye ◽  
Klaus Fraedrich ◽  
Isabella Bordi
Keyword(s):  
Climate Variability ◽  
Warm Pool ◽  
Tropical Region ◽  
Max Planck ◽  
Control Simulation ◽  
Scenario Period ◽  
The Pacific ◽  
The Future ◽  
The Mean ◽  
Regression Slopes

Abstract Climate variability is often studied in terms of fluctuations with respect to the mean state, whereas the dependence between the mean and variability is rarely discussed. Here, a new climate metric is proposed to measure the relationship between means and standard deviations of annual surface temperature computed over nonoverlapping 100-yr segments. This metric is analyzed based on equilibrium simulations of the Max Planck Institute Earth System Model (MPI-ESM): the last-millennium climate (800–1799), the future climate projection following the A1B scenario (2100–99), and the 3100-yr unforced control simulation. A linear relationship is globally observed in the control simulation and is thus termed intrinsic climate variability, which is most pronounced in the tropical region with negative regression slopes over the Pacific warm pool and positive slopes in the eastern tropical Pacific. It relates to asymmetric changes in temperature extremes and associates fluctuating climate means with increase or decrease in intensity and occurrence of both El Niño and La Niña events. In the future scenario period, the linear regression slopes largely retain their spatial structure with appreciable changes in intensity and geographical locations. Since intrinsic climate variability describes the internal rhythm of the climate system, it may serve as guidance for interpreting climate variability and climate change signals in the past and the future.

New evidence of soot particles affecting past and future cloud formation and climate

2020 ◽  
Author(s):  
Ulrike Lohmann ◽  
Franz Friebel ◽  
Zamin A. Kanji ◽  
Fabian Mahrt ◽  
Amewu A. Mensah ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Cloud Condensation Nuclei ◽  
Critical Role ◽  
Carbon Dioxide Concentration ◽  
Radiative Properties ◽  
Cloud Formation ◽  
Condensation Nuclei ◽  
Soot Particles

<p>Clouds play a critical role in the hydrological cycle and modulating the Earth’s climate via precipitation and radiative forcing. Aerosol particles acting as cloud condensation nuclei and ice nucleating particles aid in cloud formation, shaping their microphysical structure. Previously thought to be unimportant for cloud formation, soot particles that undergo oxidation by ozone and/or aging with aqueous sulfuric acid result in being both good centers for cloud droplets and ice crystals formation. However, the associated changes in cloud radiative properties and the consequences for Earth’s climate remain uncertain, because these processes have not been considered in global climate models. Here we present both past and future global climate simulations, which for the first time consider the effect of such aged soot particles as cloud condensation nuclei and ice nucleating particles. Our results constitute the first evidence that aging of soot particles produce a 0.2 to 0.25 Wm<sup>-2</sup> less negative shortwave indirect aerosol forcing compared to previous estimates. We also conducted equilibrium climate sensitivity simulations representing a future warmer climate in which the carbon dioxide concentration is doubled compared to pre-industrial levels. Accounting for these soot aging processes significantly exacerbates the global mean surface temperature increase by 0.4 to 0.5 K. Thus, reducing emissions of soot particles will be beneficial for many aspects including air pollution and future climate.</p><p> </p>

Impact of reservoir operations and climate variability on regulated flow regimes

2020 ◽  
Author(s):  
Marta Ferrazzi ◽  
Roberto Vivian ◽  
Gianluca Botter
Keyword(s):  
Climate Variability ◽  
Water Supply ◽  
Flow Regime ◽  
Flood Control ◽  
Flow Regimes ◽  
Reservoir Operations ◽  
The Mean ◽  
Annual Changes ◽  
The Impact

<p>The simultaneous growth in climate-driven fluctuations of river flow regimes and global freshwater demand threatens the security of anthropogenic and ecologic uses of streamflows. Dams have long been designed to reconcile the conflict between patterns of human water uses and the temporal variability of flows, and are operated worldwide. In this context, there is a need to understand the combined influence of reservoir operations and climate variability on regulated streamflow regimes, and disclose whether observed hydroclimatic fluctuations can be accommodated by existing reservoirs. Here, these issues are addressed through a quantitative analysis of flow regime alterations by dams as driven by heterogeneous uses and variable regulation capacities (i.e., storage capacity scaled to the average inflow). In particular, the concept of streamflow stability is used to compare inter-annual changes in the occurrence probability of synchronous flows observed upstream and downstream of dams. The selection of structures considered in this study is distributed throughout the entire Central-Eastern United States, so as to span heterogeneous hydroclimatic settings and reservoir functions (i.e., flood control, water supply, hydropower production and multi-purpose). Our results reveal that reservoirs devoted to flood control and those operating for water supply produce distinctive impacts on flow regimes. Flood control does not alter the mean discharge downstream, but decreases long-term discharge variability and, thus, homogenize regional flow dynamics. However, regulation for flood control is unable to mitigate the impact of variable climate drivers on the stability of streamflows and hydroclimatic fluctuations typical of unregulated regimes are transferred unaltered in downstream reaches, or even amplified. Water supply, instead, reduces the mean flow of regulated reaches but increases the long-term streamflow variability, thereby enhancing the regional heterogeneity of flows. In this case, regulation smooths inter-annual changes of flow regimes, though at the cost of systematically filtering out medium-to-high discharges, with negative consequences on stream ecosystems. The observed connection between reservoir functions and the features of downstream flow regime alterations by dams represents a critical step forward for a sustainable management of water resources.</p>

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