ABSTRACT
2. SimulationsThe RainMaker Humidification System (RHS) generates and delivers precise amounts of ultra pure water vapor purified for both ionic contaminants and dissolved gases. The RHS adds controlled amounts of pure water vapor directly into any carrier gas stream. It can humidify inert, corrosive, and flammable gases, such as hydrogen and oxygen, at a wide range of flow rates. The system can deliver into atmosphere as well as vacuum process pressures.Studies done by the government have shown that cool mist
humidifiers can disperse microorganisms and minerals into the air. The EPA suggests that you use a bottled distilled water in your humidifier to help lower the mineral content in the air. Also, you should not humidify indoors to over 50% as high humidity encourages growth of biological organisms, such as mold, in the home. It is suggested you keep the humidity level in your home between 35-45%.Given the proposed ACE uncertainty requirements placed on the retrieval of these and other aerosol and cloud property profiles, ACE mission planning efforts aim to systematically estimate relevant associated uncertainties in top-of-atmosphere radiative forcing as a common metric for considering the adequacy of each retrieval to meet intended scientific needs. It is our objective here to use large-eddy simulations with resolved aerosol and cloud particle size distributions to estimate the top-of-atmosphere cloud radiative forcing (CRF) associated with the specific proposed aerosol parameter uncertainties described above. We focus on broken low clouds in order to evaluate the sensitivity of cloud properties to aerosol properties below the cloud base, which are observable in cloud-free pixels among cloudy pixels by virtue of boundary layer mixing. We consider only marine clouds to limit the number of surface parameters. Wetreat all of the aerosol as ammoniumbisulfate to limit the number of aerosol composition parameters. The objective is to estimate aggregate CRF sensitivity to proposed retrieval uncertainties, including, but not limited to, any induced changes in cloud albedo, cover, and thickness.We emphasize that quantifying the potential radiative impact of anthropogenic aerosols on broken marine cloud fields is not an objective of this work. Rather, we aim only to quantify CRF sensitivity to proposed uncertainties in retrievals of specific aerosol properties. The general application in mind here is not the observational correlation of aerosol with cloud properties, but rather the constraint of aerosol properties beneath broken cloud fields in climate models, which is considered in terms of associated CRF at the local scale (over individual broken cloud fields) and at the global scale (considering the global frequency and variety of broken cloud fields). For example, what is the possible CRF uncertainty associated with an uncertainty of 50% in the effective variance of aerosols in the 0.1-1-mm size range averaged over a 500-m layer at ambient relative humidity beneath a broken marine cloud field?We are aware of no literature that quantifies the sensitivity of CRF over broken marine clouds to the specific aerosol properties targeted by ACE. There are two main barriers to adapting past work to meet the needs of this study. First, the aerosol properties targeted by ACE retrievals cannot be universally related to commonly considered aerosol properties, such as the total concentration of cloud condensation nuclei (CCN; e.g., McComiskey and Feingold 2008). CCNas a function of supersaturation is calculated during the course of the simulations here, but the inverse derivation of ACE aerosol size distribution properties from CCN requires the specification of detailed underlying aerosol and meteorological conditions. Second, observationally based studies generally rely upon the categorizing of observed conditions in terms of meteorological and cloud properties in order to isolate aerosol influences (e.g., Garrett and Zhao 2006), whereas the objective of the calculations presented here is to calculate the total CRF sensitivity to aerosol retrieval uncertainties, including the dynamical response, which cannot be assumed to be negligible (e.g., Garrett et al. 2009).The contribution of low cloud properties to both anthropogenic radiative forcing of climate and climate sensitivity has motivated extensive efforts to characterize the interactions of aerosols with low clouds and improve their representation in climate models. Whereas in situ measurements are generally most capable of characterizing localized aerosol and cloud microphysical properties in detail, routine satellite-based measurements provide long-term global coverage that is useful for constraining climate models (e.g., Quaas et al. 2009). However, a common disadvantage of satellite retrievals relative to other measurements is reduced spatial resolution and measurement sensitivity. The process of determining whether specific proposed retrievals will be adequate to meet intended scientific needs is therefore critical.It is very important that you keep your humidifier clean and follow the manufacturers suggested cleaning schedule.A proposed objective of the planned Aerosol-Cloud-Ecosystem (ACE) satellite mission is to provide constraints on climate model representation of aerosol effects on clouds by retrieving profiles of aerosol number concentration, effective variance, and effective radius over the 0.1-1-�m radius range under humidified ambient conditions with 500-m vertical resolution and uncertainties of 100%, 50%, and 10%, respectively. Shallow, broken marine clouds provide an example of conditions where boundary layer aerosol properties would be retrieved in clear-sky gaps. To quantify the degree of constraint that proposed retrievals might provide on cloud radiative forcing (CRF) simulated by climate models under such conditions, dry aerosol size distribution parameters are independently varied here in large-eddy simulations of three well-established modeling case studies. Using the rudimentary available aerosol specifications, it is found that relative changes of total dry aerosol properties in simulations can be used as a proxy for relative changes of ambient aerosol properties targeted by ACE retrievals. The sensitivity of simulated daytime shortwave CRF to the proposed uncertainty in retrieved aerosol number concentration is -15 W m^sup -2^ in the overcast limit, roughly a factor of 2 smaller than a simple analytic estimate owing primarily to aerosol-induced reductions in simulated liquid water path across this particular set of case studies. The CRF sensitivity to proposed uncertainties in retrieved aerosol effective variance and effective radius is typically far smaller, with no corresponding analytic estimate. Generalization of the results obtained here using only three case studies would require statistical analysis of relevant meteorological and aerosol observations and quantification of observational and model uncertainties and biases.“Fuel cells require feed gas to be humidified without adding any contaminants,” said Jeff Spiegelman, president of RASIRC. “Our RainMakers use high purity materials and proprietary seals, making them uniquely qualified to meet the technical challenge of unmanned humidification in space.”
The three cases of shallow, broken marine clouds developed for model intercomparison studies organized by the Global Energy and Water Cycle Experiment (GEWEX) Cloud System Study (GCSS) program are used as the basis for this study. We are aware of no other well-established modeling case studies. The cases are representative of trade wind cumuli observed during the Atlantic Trade Wind Experiment (ATEX; Stevens et al. 2001), the Barbados Oceanographic and Meteorological Experiment (BOMEX; Siebesma et al. 2003), and the Rain in Cumulus over Ocean (RICO) experiment (van Zanten et al. 2011).
Author: Fridlind, Ann M, Ackerman, Andrew S
