Astronomy

What contributes the most to the seasonal temperature variation?

What contributes the most to the seasonal temperature variation?

The seasonal temperature is ultimately due to the precession of the Earth around the axis. But what I'm curious about is… is it due more to the side experiencing winter being farther from the sun or is it more due to the fact that the days are shorter and the nights are longer?


[ The earth is actually closer to the sun in the Northern hemisphere's winter. The seasonal temperature variation is predominantly due to the angle the earth makes with the sun. In the northern hemisphere in winter the angle is such that the earth is tilted with north pole away from the sun and the sunlight hitting the earth is spread over a much larger area than if it was pointed towards the sun. Due to this tilt the sun is also lower in the sky and has the effect shown in the 2nd figure.


What contributes the most to the seasonal temperature variation? - Astronomy

We discuss the possibility of constraining the relation between redshift and temperature of the cosmic microwave background (CMB) using multifrequency Sunyaev-Zeldovich (SZ) observations. We have simulated a catalog of clusters of galaxies detected through their SZ signature assuming the sensitivities that will be achieved by the Planck satellite at 100, 143 and 353 GHz, taking into account the instrumental noise and the contamination from the Cosmic Infrared Background and from unresolved radiosources. We have parametrized the cosmological temperature-redshift law as T∝ (1+z) (1-a) . Using two sets of SZ flux density ratios (100/143 GHz, which is most sensitive to the parametrization of the T-z law, and 143/353 GHz, which is most sensitive to the peculiar velocities of the clusters) we show that it is possible to recover the T-z law assuming that the temperatures and redshifts of the clusters are known. From a simulated catalog of

1200 clusters, the parameter a can be recovered to an accuracy of 10 -2 . Sensitive SZ observations thus appear as a potentially useful tool to test the standard law. Most cosmological models predict a linear variation of the CMB temperature with redshift. The discovery of an alternative law would have profound implications on the cosmological model, implying creation of energy in a manner that would still maintain the black-body shape of the CMB spectrum at redshift zero.


The following are the factors that affect and control the annual range of temperature

The following are the factors that affect and control the annual range of temperature in the same way as they do the horizontal distribution of temperature: latitude height above the mean sea level ocean currents prevailing winds precipitation and cloudiness local relief and distance from the sea.

The height of mid-day sun is never less than at the equator. Twice in a year the sun’s rays are vertical at the equator. Thus, the temperature is uniformly high in the equatorial region, and the annual range of temperature is negligible.

But from the equator pole-ward, there is a progressive decrease in temperature. It results in greater annual range of temperature. In the Polar Regions, where the length of day and night is 6 months, one should expect the highest annual range of temperature.

But the fact is otherwise, because the low angle of incidence in the sun’s rays does not allow the temperatures to rise to higher values. Besides, a larger part of insolation received in the Polar Regions is expended in melting the ground snow.

This factor also checks any substantial rise in the temperature in those regions. Therefore the mid-latitude regions, where the seasonal variation in temperature is greatest, record the highest annual range of temperature.

Thus, it is evident that the effect of latitude on the distribution of temperature is modified to a great extent by other factors discussed below.

Height above mean sea level:

The annual range of temperature at a particular place is largely controlled by the height at which the place is situated. At high elevations, the rarity of the air, larger amount of precipitation and cloudiness combine together to lower down the average temperature even during the warmer months of the year.

But the mean values of temperature for the colder part of the year are not affected by these factors to the same degree. Thus, places situated at higher elevations have lower annual ranges of temperature.

Ocean currents:

The effects of ocean currents upon the temperature of adjacent land areas are variable, depending on the direction of prevailing winds. Where the prevailing winds are onshore, they carry the moderating effect far inland.

Under these conditions, the warm ocean currents help to raise the temperatures of the adjoining regions. For example, the prevailing westerly’s keep the winter time temperatures in Great Britain and much of the western Europe warmer for the latitude, because of the presence of the North Atlantic Drift, a warm ocean current, in the nearby ocean.

The effect of the warm ocean currents is more pronounced in winter. Hence the annual range of temperature is relatively smaller. Another example is offered by the cold ocean current of California because of which summer temperatures in the subtropical coastal Southern California are lower by 6° Celsius.

Thus, the difference between the average winter and summer time temperatures in the coastal regions of California is never large resulting in the small annual range of temperature.

Prevailing winds:

Among the factors that have controlling influence over the annual range of temperature, the prevailing winds are the most important.

Off-shore winds bring about an increase in the annual range of temperature of the adjacent land, while the on-shore winds carry the moderating influence of the oceans far inland and impose a restriction on the annual range.

The effect of ocean currents is largely determined by the direction of the prevailing winds. On­shore winds carry their influence to the coastal regions, while the off-shore winds deprive them of the warming or cooling effects of ocean currents.

Precipitation and cloudiness:

In those regions where the rains are falling or where the skies are covered with clouds, the summer temperatures are relatively lower. But during the winter, the clouds check the loss of heat by terrestrial radiation.

Thus, in cloudy regions the winter time temperatures are not allowed to fall much. Therefore in such regions the annual range of temperature is relatively smaller than those regions where the weather is clear and dry.

Local relief:

Slope is one of the potent factors which affect the temperature of a place. The slopes facing the sun have higher temperatures during summer months, and the slopes protected from the sun have much lower temperatures during winter. Thus, this local factor also affects the annual range of temperature.

Distance from the sea:

Water is heated or cooled in a longer period of time than land. Because of this peculiar characteristic of water, the coastal areas enjoy a moderate climate, and the difference in temperature of the warmest and the coldest months is not very large.

On the contrary, the interior locations have extremely hot summers and cold winters. Thus, with increasing distance from the sea-coast, there is a corresponding increase in the seasonal variation of temperatures.

However, in the vicinity of the equator the effect of distance from the sea on the annual range of temperature is quite negligible. Its effect is more marked in the temperate regions.

It may be pointed out that since the coastal locations have larger amount of clouds and the resultant precipitation, the diurnal range of temperature is also very small.


What contributes the most to the seasonal temperature variation? - Astronomy

Inspired by these comments, and I know places in the world with the largest variation has also been discussed here as a topic.

Does anyone know what climate has the absolute smallest difference between day and night, and through the year (I know any number of equatorial places, especially on oceanic islands can have temps varying 5C or less in a day, and around 2C in a year, but is there a world record for smallest difference?).

Also related would be the highest and lowest temps ever recorded, if there is data for it and anyone knows.

Equatorial islands are tough to beat in this respect. Kiribati is probably one of the leading contenders. Mean temps are the same every month of the year and the diurnal range is about 5 C. The difference between the record high and low is only about 14 C in many places in Kiribati: Extreme Temperatures Around the World- world highest lowest temperatures

There's probably a place in the world with even lower variation but you'd be hard-pressed to find it. It would probably be another equatorial island, but it could also be an equatorial highland climate with near-constant cloud cover.

Equatorial islands are tough to beat in this respect. Kiribati is probably one of the leading contenders. Mean temps are the same every month of the year and the diurnal range is about 5 C. The difference between the record high and low is only about 14 C in many places in Kiribati: Extreme Temperatures Around the World- world highest lowest temperatures

There's probably a place in the world with even lower variation but you'd be hard-pressed to find it. It would probably be another equatorial island, but it could also be an equatorial highland climate with near-constant cloud cover.

The highest *ever* recorded is 28C, the lowest 6C

I wonder if most of the population in equatorial places like Singapore would bother to check weather forecasts much, other than for rainfall, as each day should just seem the next. There shouldn't be much wind either, right?

It's weird for me to think that there are parts of the word where you would hardly need worry about how to dress before going outside. With a record low like 19C, you'd never feel cold if that's the room temperature you prefer!

I wonder if most of the population in equatorial places like Singapore would bother to check weather forecasts much, other than for rainfall, as each day should just seem the next. There shouldn't be much wind either, right?

It's weird for me to think that there are parts of the word where you would hardly need worry about how to dress before going outside. With a record low like 19C, you'd never feel cold if that's the room temperature you prefer!


The impact of climate change on astronomical observations

Climate change is affecting and will increasingly affect astronomical observations, particularly in terms of dome seeing, surface layer turbulence, atmospheric water vapour content and the wind-driven halo effect in exoplanet direct imaging.

Astronomers are entering an era in which they will change the way they work, with the arrival of the 30–40 m class ground-based telescopes and large international observational projects sparking new ways of communicating and collaborating. These scientific challenges come together with societal ones, such as the role astronomers play in communicating and undertaking actions to significantly reduce the environmental footprint of astronomical research. More generally, it is urgent that astronomers, through their unique perspective on the Universe, communicate about and act on climate change consequences at any level. In this context, we have investigated the role some key weather parameters play in the quality of astronomical observations and analysed their long-term (longer than 30 years) trends in order to grasp the impact of climate change on future observations. In what follows we give four examples of how climate change already affects or could potentially affect the operations of an astronomical observatory. This preliminary study is conducted with data from the Very Large Telescope (VLT), operated by the European Southern Observatory (ESO), located at Cerro Paranal in the Atacama Desert, Chile, which is one of the driest places on Earth. For the analyses presented below, we used the various sensors installed at Paranal Observatory but also, to show a longer time span (from 1980 to the present), we used the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate, ERA5 1 , with a spatial resolution of 31 km, which we interpolated at the Paranal Observatory location. To investigate longer timescale evolution (from 1900 to 2010), at a cost of a coarser spatial resolution (130 km) that averages the actual orography and may blend the ocean–continent interfaces, we in some cases used the ERA20C reanalysis data 2 . In addition, we explored climate projections in this region, using the Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model ensemble 3 , under the worst-case climate change Shared Socioeconomic Pathways (SSP5-8.5) scenario. Further investigation is needed to better understand the underlying mechanisms of change, as well as to assess the severity of the impact.


Numerical Models

The graphs below show the results of numeric models that calculate the dark count as a function of CCD temperature. Only the majority population of pixels is considered. The minority populations having 5, 10, 50, or more times the average dark current are not considered. Calculations were made for a Kodak KAF-0400 CCD, which has 9 micron pixels, and the SITe Si-502a CCD, which has 24 micron pixels. The Kodak models assumed a simple power law relationship with a "doubling temperature" of 5.8C. For the SITe CCD, the dark current was calculated using an exact mathematical expression that is combination of a power law and other terms. The SITe calculations per pixel were scaled down by a factor of 7.11 times to correct its larger pixel area to that of the Kodak CCD. The scaled SITe results are more directly applicable to the Kodak results, since the important quantity is not the amount of dark count per pixel, but rather the amount of dark current per unit area under an image detail appearing in the CCD frame.

The top figure below shows the model calculations for the Kodak KAF-0400 CCD. The second figure shows model calculations for the SITe Si-502a CCD chip scaled to 9 micron pixels. The SITe chip clearly has larger dark current at a given temperature, so it also has more sensitivity to temperature variations. Each graph below has two curves that define the dark current when the CCD is 0.2C warmer than average and 0.2C cooler than average. The dark count is given in units of electrons (e-). A point on a red curve indicates that the dark count is higher by that number of e- if the CCD temperature is 0.2C warmer than expected. The blue curves handle the converse case for the CCD being 0.2C colder than expected. The curves show the amount of error that would result from subtracting a dark frame taken 0.2C warmer or cooler than the CCD when the light exposure was taken. The difference 0.2C is based on the industry standard adoption of 0.1C rms temperature variation as a performance spec for CCD cameras. Therefore, one might find that the dark frame was taken when the CCD was 0.1C warmer than average, and the data frame was taken when the CCD was 0.1C cooler than average, creating a 0.2C difference in dark count. The curvature in these relationships results from the power law relationship between dark current and temperature. >

To first order, the results given here can be applied to larger temperature variations by simply scaling the result by the temperature difference. For example, to estimate the effect of 2.0C difference, multiply the graphical value by 2.0 / 0.2 = 10 times.


Astronomy 115 - Mid-Term Sample Answers

1. One of the most serious problems for the study of astrobiology is in defining what we mean by ``life'' in a way that is useful, but not overly restrictive. One consequence of this is that we often use the nature of life on Earth as a model. One fundamental aspect of terrestrial life is that our biochemistry operates in aqueous solution. Discuss the reasons why we often take this to be universal, and present possible alternatives.

All terrestrial life is based on chemical reactions in aqueous solution. Water is a unique solvent for biochemistry for the following reasons:

1) It exists in liquid phase in a broad and moderate range of temperature. Thus fluctuations in environmental temperature need to be quite large to cause liquid water to freeze or vaporize. Also, water is a liquid in a temperature range that is high enough to foster relatively fast chemical reaction rates, and low enough to allow for the existence of complex chemical compounds.

2) Water is a polar liquid, and thus allows for the construction of things like cell membranes composed of lipid-based compounds that form natural clusters in a water solution.

3) When water freezed, the resulting solid is less dense that liquid water at temperatures just above freezing. This means that ice floats, and thus provides thermal insulation to allow the persistence of liquid water underneath ice layers.

A number of other volatile compounds could, potentially, also be used as liquid solvents for biochemistry. The most common of these are ammonia, methane and ethane. All of these are liquids over much smaller ranges of temperature, and at much lower temperatures than water. Thus they are not as good from a thermal stability standpoint, and any biochemistry occuring in such solutions would have very slow reaction rates. Further, none of these are polar liquids. Thus the nature of the structural chemistry of any life in, say, ammonia solution, would have to be very different that the structural chemistry used for terrestrial life. Finally, ices of these compounds are all more dense than the corresponding liquids. Thus if conditions are sufficiently cool to allow for freezing, the end result is a fully frozen environment, as no surface insulation layer can form.

2. People often have the notion that ``extraterrestrial life'' means intelligent, technologically advanced aliens. Consider the history of life on the Earth, and use that to present an argument that most extraterrestrial life is likely to be neither technologically advanced nor intelligent.

Evidence of life on the Earth goes back to at least 3.5 Gyr ago. Up until about 500 Myr ago, all terrestrial life forms were single-celled organisms. The first evidence of what something like intelligent hominins dates back no more than 3 Myr ago. The first cities arose about 5000 years ago. Technology, of the sort required for communication across interstellar distances, has only existed for a bit more than a century at this point.

This means that intelligent, technologically advanced life has only existed on the Earth for about a part in a 100 million of the entire history of life on the Earth. If the development of life on the Earth is anything like typical, this means that the vast majority of extraterrestrial life will not likely be intelligent, technologically advanced life, but will more likely be single-celled organisms.

One thing that could make the possibility of intelligent, technologically advanced aliens more likely is that such civilizations could last a very long time. While we have only had the technology for interstellar communication for a century or so, it is possible that we could continue to have it for as long as billions of years. If technologically advanced civilizations last a very long time, this would increase the odds for our finding it.

3. How and why is the existence of extremophile life on Earth an important guide for our search for life elsewhere in the Universe? Give examples of types of extremophiles and of extraterrestrial environments that are similar to those in which these extremophiles thrive.

The existence of extremophile life demonstrates that life can adapt to a range of conditions far wider than was understood a few decades ago. Thus it guides us to consider a much broader range of environments as potentially life-bearing than we might otherwise.

Thermophile colonies surrounding ocean bottom thermal vents represent entire ecosystems that do not require energy input from the Sun to persist. Thus they demonstrate that life could exist in similar environments at the bottom of the Europa sub-surface ocean.

Life is also found in the Antarctic dry valleys, and in deep subsurface rocks. The surface of Mars is as cold and dry as the Antarctic dry valleys, although the atmospheric pressure is lower and the uv flux much higher. Even so, if life were to have arisen during an earlier, warmer, wetter phase of Martian history, it is possible that it could persist in subsurface rocks, just as lithophile life on Earth is able to.

4. We now know of more than 4000 planets orbiting other stars. What method was used to discover the majority of these planets, and how does it let us determine the properties of those planets?

Most known extrasolar planets have been discovered using the transit method. If a planet passes directly in front of a star the planet will block a small fraction of the light from the star. Thus, if we monitor the brightness of a star and look for periodic events in which the star becomes slightly dimmer, we can detect the presence of the orbiting planet. This method will only work if the planetary orbit plane is edge-on to our line of sight, so we expect only a few percent of stars with planets to show evidence of transits.

As the transits are periodic, they yield the period of the orbit directly. The amount of the star's light that is blocked tells us the ratio of the size of the planet to the size of the star (the bigger the planet the more light it blocks). If we also know the size of the star, we can use this to determine the size of the planet. An edge-on orbit also allows us to measure the radial velocity variation of the host star accurately. We also know the orbit period, as noted above. If we also know the mass of the star, then we can determine the mass of the planet from the orbit characteristics. Knowing both the size and the mass of the planet allows us to determine its density as well. As rocky planets and gas planets have very different densities, we can use the density to tell us what the nature of the planet is.


Data availability

The VIRTIS calibrated data are publicly available through the ESA’s Planetary Science Archive (PSA) website (https://archives.esac.esa.int/psa/) and NASA’s Planetary Data System (https://pds.nasa.gov/) in accordance with the schedule established by the Rosetta project. Other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. Readers are welcome to comment on the online version of the paper.


Solar radiation

Nuclear fusion deep within the Sun releases a tremendous amount of energy that is slowly transferred to the solar surface, from which it is radiated into space. The planets intercept minute fractions of this energy, the amount depending on their size and distance from the Sun. A 1-square-metre (11-square-foot) area perpendicular (90°) to the rays of the Sun at the top of Earth’s atmosphere, for example, receives about 1,365 watts of solar power. (This amount is comparable to the power consumption of a typical electric heater.) Because of the slight ellipticity of Earth’s orbit around the Sun, the amount of solar energy intercepted by Earth steadily rises and falls by ±3.4 percent throughout the year, peaking on January 3, when Earth is closest to the Sun. Although about 31 percent of this energy is not used as it is scattered back to space, the remaining amount is sufficient to power the movement of atmospheric winds and oceanic currents and to sustain nearly all biospheric activity.

Most surfaces are not perpendicular to the Sun, and the energy they receive depends on their solar elevation angle. (The maximum solar elevation is 90° for the overhead Sun.) This angle changes systematically with latitude, the time of year, and the time of day. The noontime elevation angle reaches a maximum at all latitudes north of the Tropic of Cancer (23.5° N) around June 22 and a minimum around December 22. South of the Tropic of Capricorn (23.5° S), the opposite holds true, and between the two tropics, the maximum elevation angle (90°) occurs twice a year. When the Sun has a lower elevation angle, the solar energy is less intense because it is spread out over a larger area. Variation of solar elevation is thus one of the main factors that accounts for the dependence of climatic regime on latitude. The other main factor is the length of daylight. For latitudes poleward of 66.5° N and S, the length of day ranges from zero (winter solstice) to 24 hours (summer solstice), whereas the Equator has a constant 12-hour day throughout the year. The seasonal range of temperature consequently decreases from high latitudes to the tropics, where it becomes less than the diurnal range of temperature.


Melatonin and the Endocrine Role of the Pineal Organ

III Melatonin Metabolism

Since the pineal makes melatonin and stores and metabolizes very little of it ( Wurtman et al., 1968c) , the diurnal variations in melatonin biosynthesis and in pineal melatonin content presumably indicate phasic secretion of the methoxyindole from the pineal. Moreover melatonin has been found in urine and plasma (where it exhibits 24-hour variations) ( Pelham et al., 1972 , and is also present in tissues which lack the enzymes necessary to synthesize it. However, sensitive and simple techniques are not yet available for assaying melatonin in small amounts of peripheral blood or in venous blood from the pineal (for discussion see Cardinali and Wurtman, 1974c ). Hence it is not yet possible to determine the in vivo rate of melatonin secretion from the pineal. As little as 10 −13 gm/ml of melatonin is detectable by bioassay (which depends on the ability of the hormone to blanch isolated skin of Rana pipiens, or intact, live, Rana pipiens or Xenopus laevis larvae), but these methods are not sensitive enough to detect the tiny amounts of melatonin likely to be present in the cerebrospinal fluid (CSF), or in plasma during the light period of the day. It seems safe to predict, however, that the development of more sensitive techniques at the subpicogram level, e.g., gas chromatography-mass spectrometry ( Cattabeni et al., 1972 ) and radioimmunoassay, will close the gap that separates the considerable knowledge on melatonin biosynthesis from the uncertainty concerning melatonin dynamics in the body.

Controversy continues over the body fluid or fluids into which the mammalian pineal secretes melatonin. It has been suggested that melatonin is secreted into the CSF ( Wurtman and Antón-Tay, 1969 ). The close juxtaposition of the ventricular system and the pineal parenchyma observed in certain species ( Sheridan et al., 1969 Quay, 1970 ), but not in other species ( Smith, 1971 ), tends to support this speculation however it seems unlikely that anatomical approaches will be able to resolve this question.

If isotopically labeled melatonin is injected into the venous blood the hormone enters all tissues, including the brain ( Kopin et al., 1961 Wurtman et al., 1964 ). Labeled melatonin injected into the CSF is taken up unevenly by the brain it becomes concentrated within the hypothalamus and the midbrain ( Antón-Tay and Wurtman, 1969 Cardinali et al., 1973a) . Melatonin has been identified in the rat hypothalamus by gas chromatography-mass spectrometry ( Green et al., 1972 ). These regions of the brain are considered possible sites of action for methoxyindoles since the administration of melatonin rapidly elevates the hypothalamic and midbrain serotonin levels ( Antón-Tay et al., 1968 ) and inhibits hypothalamic protein synthesis ( Orsi et al., 1973 ). Administration into the CSF raises brain melatonin- 3 H levels several hundred times higher than systemic administration ( Antón-Tay and Wurtman, 1969 ).

Little information is available concerning the metabolic fate of melatonin in the brain. Melatonin- 3 H taken up from the CSF disappears rapidly from the brain ( Cardinali et al., 1973a) . Its decay exhibits two major components, i.e., an early phase lasting 20 minutes, and a second, slower single-exponential component with a half-life of about 40 minutes. The prior intracisternal administration of nonlabeled melatonin decreases the melatonin- 3 H and labeled melatonin metabolites remaining in the brain 1 hour later ( Cardinali et al., 1973a) . These data indicate that the capacity of the brain to take up and retain melatonin may be saturable moreover they suggest that the melatonin metabolites found are actually formed within the brain. Exposure of rats to continuous light or darkness not only affects pineal melatonin biosynthesis (see above) but also modifies the metabolism of exogenous melatonin in the brain ( Cardinali et al., 1973a) and the ovary ( Wurtman et al., 1964 ).

Melatonin ultimately enters the general circulation most of the hormone in plasma (60-80%) is bound to serum albumin ( Cardinali et al., 1972c) . This complex is readily dissociable, however, and the presence of the binding protein apparently does not modify the biological activity of melatonin. Although the central nervous system actively metabolizes melatonin (through yet undefined pathways), the liver appears to be the major site of melatonin inactivation in the body the methoxyindole is first hydroxylated to 6-hydroxymelatonin by a microsomal NADPH-requiring enzyme ( Kopin et al., 1960 ), and this hydroxylated product is then conjugated with glucuronic or sulfuric acid and excreted into the urine. Chlorpromazine and other phenothiazines delay the disappearance of isotopically labeled melatonin from blood and tissues, probably by inhibiting the metabolism of melatonin in the liver ( Wurtman et al., 1968d) .