Forbidden Ca ii in the Sun unmasked by way of Venus

Eleven high-dispersion spectra of Venus, taken with blue Doppler shifts have enabled us to unmask the 7323.88 Å forbidden line of Ca ii from terrestrial absorption. We obtain an equivalent width of 7.4±0.4 mÅ for this line in integrated sunlight. Our value of W _λ is smaller than previous values and much more accurate. The HSRA solar model gives a solar calcium abundance of A _Ca = 6.21.     

Semiperiodic variations in CO2 abundance on Venus

Photoelectric spectral scans of the P branch of the 8689 Å CO₂ band on Venus were made using the 107-inch coude scanner during seven observing periods in the past 2 years. The relative CO₂ line strength was determined for each scan, then normalized to remove the spatial variations leaving only temporal variations.The 4-day periodicity in the relative CO₂ line strength noted by Young et al. (1973) is not unique; we do confirm their 4-day periodicity in August 1973. Four other observing periods rule out a 4-day periodicity.A definite North-South asymmetry in the relative CO₂ line strength is noted during 1973, in most cases with the same periodicity present in both hemispheres. When the slit positions are referred to the equator of Venus, particularly near inferior conjunction, the large asymmetrics between the slit positions can be explained by a greater CO₂ line strength over the polar regions and weaker over the equatorial latitudes. The amplitude of variation of each position on the crescent is much greater near inferior conjunction either because we are sampling a smaller area on the planet or because the upper atmospheric abundance is more sensitive to the mechanism causing the variation in the smaller regions sampled at inferior conjunction.Simultaneous H₂O measurementsduring several of the observing runs indicate a lack of correlation in the relative CO₂ line strengths and the H₂O abundance.     

The inclination function in terms of nonsingular elements

Different formulas for computation of the inclination function in terms of nonsingular elements have been presented and compared. Among the ways to compute the inclination function presented below, the best one is based on the recurrence relations (eqs. 16) derived in this paper.     

On accumulation of water substance in a column of rising air

Abstract

The accumulation of condensed water in moist rising air is discussed in relation to the ratio of the air speed co the fall speed of precipitation. The maximum ultimate accumulation occurs when that ratio is near unity; the duration of a transient phase is proportional to the inverse of the fall speed of precipitation when updraft are weak, and to the inverse of air speed when the air speed is moderate or strong. The kinematic framework presented has dynamical implications that help explain some behaviour of showers and storms.     

Significance of model credibility in estimating climate projection distributions for regional hydroclimatological risk assessments

Ensembles of historical climate simulations and climate projections from the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset were investigated to determine how model credibility affects apparent relative scenario likelihoods in regional risk assessments. Methods were developed and applied in a Northern California case study. An ensemble of 59 twentieth century climate simulations from 17 WCRP CMIP3 models was analyzed to evaluate relative model credibility associated with a 75-member projection ensemble from the same 17 models. Credibility was assessed based on how models realistically reproduced selected statistics of historical climate relevant to California climatology. Metrics of this credibility were used to derive relative model weights leading to weight-threshold culling of models contributing to the projection ensemble. Density functions were then estimated for two projected quantities (temperature and precipitation), with and without considering credibility-based ensemble reductions. An analysis for Northern California showed that, while some models seem more capable at recreating limited aspects twentieth century climate, the overall tendency is for comparable model performance when several credibility measures are combined. Use of these metrics to decide which models to include in density function development led to local adjustments to function shapes, but led to limited affect on breadth and central tendency, which were found to be more influenced by “completeness” of the original ensemble in terms of models and emissions pathways.     

The Effects of Reduced Tidal Flushing on Mangrove Structure and Function Across a Disturbance Gradient

The effects of reduced tidal flushing on post-hurricane mangrove recovery were measured across a gradient of hurricane disturbance (in order of decreasing wind intensity: Captiva, North Sanibel, Central Sanibel, and East Sanibel). Each region consisted of replicate study plots with either reduced tidal exchange (tidally restricted location) or an open tidal connection (tidally unrestricted location). Locations with reduced tidal exchange displayed significantly lower (two-way ANOVA, p ≤ 0.0001) tidal amplitude, decreased seedling densities, and decreased productivity (recruitment, growth, and litter fall) when compared to the tidally unrestricted locations. Results also indicated significant regional variations in measures of mangrove stand structure (seedlings and canopy) and productivity (recruitment, growth, and litter fall) up to 4-years post-hurricane disturbance. These findings suggest that the legacy effects from hurricane disturbance vary with degree of wind intensity, acting both independently and synergistically with the effects of tidal restriction to influence post-hurricane mangrove structure and function.