Description: Archaeological records document a significant expansion of populations from the Last Glacial Maximum (LGM, ~23-19 ka) to the early Holocene (EH, ~9 ka) in Eurasia, which is often attributed to the influence of orbital-scale climate changes. Yet, information remains limited concerning the climatic factor(s) which were responsible for conditioning demographic patterns. Here, we present results from an improved Minimalist Terrestrial Resource Model (MTRM), forced by a transient climate simulation from the LGM to the EH. Simulated potential hunter-gatherer population densities and spatial distributions across Eurasia are supported by observed archaeological sites in Europe and China. In the low latitudes, potential population size change was predominantly controlled by precipitation and its strong influence on plant and animal resources. In the middle-high latitudes, temperature was the dominant driver in influencing potential population size change and animal resource availability. Different regional responses of potential populations to climate change across Eurasia - owing to variations in available food resources between the LGM and EH - provide a better understanding of human dispersal during the Late Pleistocene.

Description: The mass loss in the Greenland Ice Sheet (GrIS) has significant impacts on sea level rise, water cycle balance, and even global climate stability. The Gravity Recovery and Climate Experiment (GRACE) satellites are widely utilized to investigate the GrIS mass changes, but its spatial resolution is limited, resulting in large signal leakage into the ocean and the interior of GrIS. Therefore, we proposed a novel weighted forward modeling (WFM) method, which treat the high spatial resolution surface elevation change data driven by the satellite altimetry as spatial weighting factors to pinpoint total mass change form satellite gravimetry. To understand the performance of the novel WFM method, we design close-loop numerical study, which shows that WFM method has better spatial distribution accuracy, correlation and root mean square error (RMSE) than the ordinary forward modeling (FM) method. In the real data analysis, the WFM method was used to estimate the high-resolution mass changes of GrIS and its 19 sectors from 2003 to 2017. The independent mass balance data based on the Input-output method is utilized for verification, and compared with the FM method. The results showed that the average trend bias of the WFM method was 5.8 Gt/yr and the average RMSE was 25.4 Gt, which improved by 27.8% and 26.8% relative to the FM solution. And the WFW based on solutions are in good agreement with the mascon products released by CSR, JPL and GSFC. The WFM solution can improve our understanding of the small-scale GrIS mass variation characteristics.

Description: The current progress of optical clocks has reached a fractional frequency uncertainty of 1.0x10〈sup〉-18 〈/sup〉which corresponds to a geopotential difference of 0.1 m〈sup〉2〈/sup〉/s〈sup〉2〈/sup〉. Those gravitational potential differences can be observed as gravitational redshift when comparing the frequencies of optical clocks. Even temporal potential variations might be determined with precise optical clocks on low-orbiting satellites, e.g., at altitudes of SLR-like (e.g. LAGEOS-1/2), GRACE-like and GOCE-like missions.〈sup〉〈/sup〉In this simulation study, the potential of space-borne precise novel optical clocks for the determination of temporal variations of low-degree gravity field spherical harmonic coefficients will be discussed. We will demonstrate that optical clocks at current achievable level of uncertainty are able to reveal long-wavelength seasonal and secular gravity changes. Different configurations of satellite orbits, i.e. at different altitudes (between 250 and 6000 km) and inclinations, are selected as well as certain assumptions on the clock performance are made. We will quantify how well degree-2 coefficients can be estimated from those optical clock measurements and how it compares to results from SLR data. Keywords: Optical clock measurements in space, temporal long-wavelength Earth’s gravity field variations, Relativistic Geodesy Acknowledgements: This research was funded by the German Research Foundation (DFG) under Germany’s Excellence Strategy EXC 2123 QuantumFrontiers (Project-ID 390837967) and the Collaborative Research Centre CRC-1464 “TerraQ - Relativistic and Quantum-based Geodesy”.

Description: Kinetic Alfvén waves (KAWs) are ubiquitous throughout the plasma universe. Although they are broadly believed to provide a potential approach for energy exchange between electromagnetic fields and plasma particles, neither the detail nor the efficiency of the interactions has been well-determined yet. The primary difficulty has been the paucity of knowledge of KAWs’ spatial structure in observation. Here, we apply a particle-sounding technique to Magnetospheric Multiscale mission data to quantitatively determine the perpendicular wavelength of KAWs from ion gyrophase-distribution observations. Our results show that KAWs’ perpendicular wavelength is statistically 2.4±0.7 times proton thermal gyro-radius. This observation yields an upper bound of the energy the majority proton population can reach in coherent interactions with KAWs, that is, roughly 5.76 times proton perpendicular thermal energy. Therefore, the method and results shown here provide a basis for unraveling the effects of KAWs in dissipating energy and accelerating particles in a number of astrophysical systems, e.g., planetary magnetosphere, astrophysical shocks, stellar corona and wind, and the interstellar medium.

Description: An accurate model of the Earth’s gravity field is beneficial for practical engineering and many applications in geosciences. ESA realized the GOCE gradiometry mission between 2009 and 2013. However, the observation accuracy of the GOCE mission suffered greatly due to the low-frequency drift of the onboard electrostatic accelerometers. Advances in electrostatic and quantum technology offer new measurement concepts for future gradiometry missions. In this study, we evaluate the contributions of several types of accelerometers through numerical closed-loop simulation which rigorously maps the accelerometers’ sensitivities to the gravity field coefficients. In comparison to the simulated results of the GRADIO gradiometer used in GOCE, it is demonstrated that the MicroSTAR-type gradiometer has superior precision up to degree and order 100 and provides more signal information in the off-diagonal components of the gradient tensor. The precision of the gravity field model recovery using a hybrid gradiometer that includes quantum technology can benefit from the applied cold atom interferometry (CAI). A hybrid gradiometer with a CAI performance up to 10^-11m/s^2/Hz^1/2 will increase the retrieval of the gravity field remarkably. With an orbital rotation compensation mechanism, the CAI gradiometer can perform with higher accuracy than a classical instrument alone. If not, the accuracy when using the hybrid gradiometer might only be superior up to degree and order 50.

Description: The radiative properties and lifetime of mixed-phase clouds are strongly influenced by ice formation, and the formation of secondary ice in clouds is one of the longest-standing problems in cloud physics. In DCMEX we conducted multiple flights over New Mexico in the Magdalena Mountain region to provide high-resolution cloud microphysical and aerosol measurements to provide information on the temporal and spatial distribution of ice phase evolution and the linkage between convective cloud thermodynamic and secondary ice processes. We used a combination of high-resolution instruments (including 3VCPI, 2DS, HVPS, and CDP) to provide measurements of the evolution of cloud particle and precipitation concentrations, sizes and morphology to identify and assess primary and secondary ice production contributions as well as where precipitation particles first form and how they develop. The initial results suggest the principal secondary ice production mechanism in these clouds was ice splinter production during riming (Hallet-Mossop) but other production mechanisms were also contributed. Our next step is to combine these data with the cloud thermodynamic background confirming the occurrence of secondary ice and identifying the conditions for the formation of secondary ice. In addition, the aerosol data including cloud particle chemical composition will be used to investigate and quantify their contribution to primary ice formation.

Description: Detecting changes in runoff and sediment in the Loess Plateau is a hot issue. The Kuye River located in the Loess Plateau was selected as a typical Basin. Based on the observed hydro-meteorological data during 1960—2014, there was a statistically significant increasing trend in annual mean temperature, an insignificant decreasing trend in annual precipitation, and significant decreasing trends in annual runoff and sediment. 1980 and 1999 were two breakpoints of the relationships among runoff, sediment and climatic factors. The ensemble modelling framework of runoff and sediment was constructed by the VIC model and eight sediment models based on machine learning algorithm. The Nash-Sutcliffe efficiency coefficient and correlation coefficient for monthly runoff and sediment simulation were higher than 0.6 and 0.7, respectively, that denoted acceptable performance. Based on the comparison between the reconstructed natural runoff and sediment versus observed values, the attribution of runoff and sediment changes were quantitatively analyzed. The results indicated that the contributions of climate change and human activities to runoff reduction in 1980—2014 were 25%-40% and 60%-75% respectively, and the contributions to sediment reduction were 15%-36% and 64-85%, respectively, compared with that in the natural period from 1960 to 1979. Human activities are the main reason for the decreases in runoff and sediment in the Kuye River basin. The related results could improve an innovative methodology to understand the attribution of runoff and sediment changes.

Description: Numerous studies have indicated that the atmospheric heat source (AHS) over the Tibetan Plateau (TP) is highly correlated with the western North Pacific anomalous anticyclone (WNPAC) in summer. However, such an interannual relationship has been weakened since the late 1990s. The present work shows that the TP AHS was significantly and positively correlated with the WNPAC in 1979–1999 (P1), while this relationship became insignificant hereafter (2000–2020; P2). We identify that the long-term change in the upper-level atmospheric circulation over the TP is responsible for weakening the relationship. An obvious upper-level anticyclonic trend occurred over the northeastern TP in the past four decades, with an easterly trend on the anticyclone’s southern flank, representing anomalous westerlies during P1 but anomalous easterlies during P2 over the main portion of the TP. With the anomalous upper-level westerlies in P1, the abnormal high pressure induced by the TP heating (i.e. AHS) extended downstream in the upper troposphere. Subsequently, anomalous descending motions formed over the northwestern Pacific due to the eastward-extended high pressure, together with the vertical transport of negative relative vorticity, favorable for the enhancement of the WNPAC. Whereas in P2, the TP heating-induced abnormal high pressure was confined over the southern TP due to the anomalous easterlies, suppressing its downstream influence and finally breaking the connection between the TP AHS and the WNPAC. Modeling results from both LBM sensitivity experiments and CESM large ensemble dataset further confirm the important role of the change in background circulation in weakening the relationship.

Description: Salt-tide invasion in the dry season seriously threatens freshwater availability in a tidal river area. Freshwater availability is associated intensely with natural factors and human activities. Therefore, a new framework, i.e. regulation by avoiding saltwater withdrawal (RASW), which developed relationships among saltwater intrusion, upstream streamflow and local water supply, was established. The RASW contains three phases, i.e. estuary salinity-exceedance simulation, upstream streamflow distribution design, and local water supply security analysis, which was applied in Zhuhai-Macao water supply system of the Guangdong-Hong Kong-Macao Great Bay Area, China. Results demonstrate that a hybrid data-driven method coupling wavelet transform and random forest was more accurate for the salinity-exceedance simulation. Upstream streamflow and the time of excessive salinity in the waterway were connected, and the time of withdrawal avoiding saltwater was obtained. Critical upstream streamflow for various scenarios of water demand in the dry season were identified. However, the security of water supply is majorly associated with the distribution of upstream streamflow in the dry season. The meta-Gaussian copula efficiently simulates the six-dimensional distribution of monthly streamflow and is appropriate for design streamflow distribution. Water supply security benefits greatly from the joint river-reservoir regulation mode. For a given exceedance frequency of average streamflow, the modes and security situations are diverse, due to various streamflow distributions, i.e. extreme low streamflow and its occurrence time. The proposed framework facilitates integrated decision-making for water supply security in coastal area.