High level clouds and surface temperature

Guest post by Erl Happ

The orbit of the Earth’s around the sun is slightly eccentric. The closest point is called the perihelion. On January 4th the Earth is just 147,098,291 km away from the sun. Aphelion occurs July 4th when the Earth is 152,098,233 km away from the sun, a difference of +3.3%. Naturally the power of the sun falls away with distance. Its radiation is 7% weaker in July than in January. Strangely, near surface air temperature for the Earth as a whole is 3.3°C warmer in July than in January. Yes, the surface is warmest when the Earth is furthest from the sun!

On a hemispherical basis total cloud cover increases as the surface warms but the loss of cloud in the southern hemisphere as the south cools and the north warms is much greater than the gain of cloud in the northern hemisphere. So, on a global basis cloud cover falls in mid year. Total cloud cover tells us nothing about global albedo because different types of clouds vary in their albedo and the mix of cloud types changes. Some cloud is actually supposed to trap radiation and warm the surface and this type changes a lot.

On the face of it, the warming process that occurs in mid year is only limited by the fact that the Earth moves about the sun on its tilted axis allowing cloud cover to recover between November and March.

This post explores where, why and what sort of cloud is lost as the global atmosphere warms in mid year. It turns out that there is a heavy loss of high level cloud in the southern hemisphere. The manner in which this loss occurs informs us as to the role of outgoing radiation in the climate system, the artificiality of our notions of what constitutes the troposphere and the stratosphere and the dynamics of the system that determines surface temperature and its variability from year to year and over time. It tells us about the impact of high cloud on surface temperature. The ‘natural’ dynamics described in this post are currently unrecognized in climate science as it is represented in UNIPCC reports.

All data for the graphs from http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl

Figure 1 Surface air temperature (°C) and precipitable water (kg/m^2). Percentage change between minimum and maximum is indicated.

The increase in precipitable water lags the temperature increase by a couple of months. There is plainly more variability in the land rich northern hemisphere.

The maps below come from the invaluable JRA-25 Atlas at: http://ds.data.jma.go.jp/gmd/jra/atlas/eng/atlas-tope.htm

Figure 2 Total cloud cover January

Figure 3 Total cloud cover July

It is evident that all the driest parts of the land in both hemsipheres have less cloud in July than they do in January. These dry locations are sources of potent surface radiation. There is less cloud as a whole in July (more dark blue) than in January. There is more dark blue between the equator and 30° south in southern winter (July) than in summer. But what type of cloud is lost?

Cloud is classified according to elevation:

High cloud 7.6km to 12 km (300hPa to 150hPa)

Medium level cloud 2.4 to 5.5km (700 to 400hPa)

Low cloud below 2.4km. Below 700hPa.

Figure 4 Annual cycle of relative humidity at 10-30°south and 10-30°north at 925hPa (near surface) and at 300hPa (8km)

In the topmost figure we see a marked reduction in relative humidity at 300hPa at 10-30° south in mid year. The same latitudes in the northern hemisphere experience an increase in relative humidity in mid year.

In the lowest figure we see only a slight reduction in relative humidity at 925hPa affecting the last half of the year. However there is a loss of humidity in the middle of the year that increases with altitude. Notice that humidity at 300hPa generally exceeds that at 700hPa and 500hPa.

Figure 6 Relative humidity between 50°north latitude to 50° south latitude

Figure 6 aggregates data for all latitudes between 50° north and 50° south. There is a gradual but small decline in relative humidity in the low cloud zone at 850hPa towards a low point in mid year. We see a marked trough in relative humidity at 300hPa between April and November. This establishes that the main inter-seasonal dynamic occurs in the upper troposphere. But at what latitude?

Figure 7 Relative Humidity by latitude

Figure 7 reveals that the slight loss of relative humidity at 850hPa between 50°north and south latitude is a product of diverse trends.

It is plain that the mid year loss of humidity at 300hPa that characterizes the latitude 50°north to 50° south as a whole is is driven by marked change in the southern hemisphere.

Why is it so?

Figures 8 and 9 illustrate the point that the great high pressure cells of the Hadley circulation produce copious amounts of thermal (infrared) radiation colored red. This is particularly the case in the winter hemisphere. Here is a conundrum. Why do the subtropical latitudes of the winter hemisphere give off more radiation when the surface is cooler than when it is warmer?

First, what’s a Hadley cell? At the equator the air ascends. As it ascends latent heat is released, the air becomes less dense is driven upwards and in the process it cools via decompression. Hence the paucity of outgoing radiation in near equatorial latitudes. The warm waters between India and New Guinea give off little radiation but they deliver much evaporation. Air that ascends at the equator ultimately returns to the surface at 10-40° of latitude. It descends over cool surfaces that support the process of descent by cooling the surface air. The sea is cooler, and the land is much cooler in winter. Extensive high pressure cells circulate anticlockwise in the southern hemisphere and clockwise in the northern hemisphere giving rise to the trades and the westerlies. These cells are largely free of low and middle troposphere cloud. The air in these cells warms via compression, the bike pump effect. So, as these high pressure cells occupy more space in the winter hemisphere the surface must receive more direct sunlight and the winter hemisphere at these latitudes must be warmer than it otherwise would be.

Figure 8 July outgoing long wave radiation

Figure 9 January outgoing long wave radiation

It is apparent that atmospheric processes determine where thermal radiation is released by the Earth system. It is released from the atmosphere rather than directly from the surface. The area of cloud free sky tends to be enhanced in winter. This must be considered a positive. We like to be warmer in winter. If this is what the greenhouse effect is all about I am all for it. But hang on, the greenhouse effect must be quite weak because there is little chance of water vapor amplification in dry air. What a bummer.

Figure 10 Air temperature at various elevations at 20-30°south

Figure 3 shows that the temperature of the upper troposphere at 20-30° south responds to enhanced radiation in winter just like the stratosphere at 50hPa. The response depends upon the ability of ozone to trap long wave radiation at a quite specific wave length, 9.6 micrometers. Infrared spans 4-28 micrometers. We see a strong response to just a small part of the total spectrum by a mass of tiny little radiators that populate this part of the atmosphere in the parts per billion range but sufficient to invert the seasonal temperature profile. Hang on, this is not in the rule book, the troposphere is supposed to be warmed from the surface and should move with surface temperature! But here we see the upper troposphere acting like the stratosphere in that it responds to long wave radiation. Do we need to alter our ideas of what the stratosphere starts? Where is the ozone tropopause?

A winter warming response at 250hPa, involving a marked loss of relative humidity in the ice cloud zone, tells us that the moisture supply to the upper troposphere is disconnected from the temperature dynamic at this altitude. Quite possibly, the supply of moisture to the upper troposphere in the southern hemisphere depends upon the temperature of the tropical ocean that falls to its annual minimum in mid year. Quite possibly, that moisture is moving north rather than south in mid year.

Climatologists have long wondered why a 1°C increase in temperature at the sea surface relates to as much as a 3° increase in temperature of the upper troposphere. They call this phenomenon ‘amplification’ as if the temperature of the upper troposphere in some way depended on the temperature at the surface and there was a transistor circuit between the two. Hey guys, its the other way round. Turn the telescope round. The presence of a long wave absorber namely ozone, is responsible for this phenomenon. The warming of the upper troposphere results in cloud loss and then, after a little time lag, the surface temperature increases.

In the mid and high zone, cloud is present as highly reflective interlacing micro-crystals of ice that we describe as cirrus and stratus. When the air warms these crystals sublimate. Ice cloud is the dominant cloud of the subtropical region. In IPCC climate science high altitude ice cloud is supposed to warm the surface by enhancing back radiation. But when radiation from the atmosphere increases in winter relative humidity falls. This radiation it is not bounced back by the cloud, the cloud disappears and lets the sun shine through. The surface temperature response is due to the disappearance of the cloud, not back radiation. Oops.

Figure 11 Southern Hemisphere locations exhibiting high altitude ice cloud on 26th September 2011

The evolution of surface temperature is intimately related to the coming and going of clouds. The animation at http://www.intelliweather.com/imagesuite_specialty.htm

reveals that the circulation of the air in the high cloud zone is independent of and quite contrary to the low cloud zone.

Figure 12 High cloud cover in January and July Source JRA-25 Atlas at http://ds.data.jma.go.jp/gmd/jra/atlas/eng/atlas-tope.htm

Figure 12 shows the latitudes of the southern hemisphere where high cloud is evaporated in July. There is a marked expansion in the area that has less high cloud by comparison with January.

Figure 13 The advance of global temperature in January and July

Figure 13 indicates that there is more year to year variability in the minimum global temperature (January) than the maximum (July).

The minimum is experienced when the Earth is closest to the sun. The Earth is coolest at this time because the atmosphere is cloudier in January. January is characterized by a relative abundance of high ice cloud in the southern hemisphere. Relative humidity peaks in April (figure 6) when tropical waters are warmest. I suggest the variation in the minimum global temperature is due to change in high altitude cloud. The southern hemisphere experiences the largest flux in ice cloud.That flux in high cloud is likely to be due to change in ozone content of the upper troposphere.

Variation in cloud cover should be the first hypothesis to explore when the Earth warms or cools over time. You would have to be very naive to think that the inter-annual change in temperature that is most obvious between November and March could be due to something other than a change in cloud cover.

Figure 14 Temperature of the sea and the upper troposphere at 250hPa at 20-30° south in January.

Figure 15 Temperature of the sea and the upper troposphere at 250hPa at 20-30° south in July.

In January we observe a close relationship between the temperature of the upper troposphere at 20-30°south and the temperature of the sea. The so called ‘amplification factor’ is plainly there.

In July we see a decline in 200hPa temperature between 1948 and 1978 in line with the decline in the temperature of the northern hemisphere during that interval and a strong increase in 200hPa temperature after 1978 as the northern hemisphere warmed strongly. We know that the temperature of the stratosphere at 20-30°south is linked to the extent of warming in the northern hemisphere in mid year. The greater the convectional updraft that occurs north of the equator in mid year, the more voluminous is the stream of air that descends in the winter hemisphere. So, as the north warms the greater will be the outgoing radiation and the warmer will be the stratosphere and the upper troposphere in the southern hemisphere. The warmer it is, the less extensive must be the reflective ice cloud.

Figure 16 Anomalies in temperature at 200hPa, 300hPa and at the sea surface 20-30° south. Three month moving averages of monthly data.

Looking now at departures from the 1948-2011 monthly average the dependance of surface temperature upon upper troposphere temperature is plain to see. In a warming cycle we see 200hPa temperature rising above 300hPa and sea surface temperature and falling below it in a cooling cycle. The shift of in 200hPa temperature between 1976-1980 had its origins in the increase in the temperature of the Antarctic stratosphere at that time and the commencement of the warming in the northern hemisphere.

The $64,000 question is what causes the change in the ozone content of the high cloud zone between November and March when the greatest variability in global surface temperature is seen.

The $164,000 question is what is causing cloud cover to rise and fall on decadal and centennial time scales.

The answer to both questions lies in the activity of the coupled circulation of the stratosphere and the troposphere at the poles that feeds ozone into the troposphere. The upper troposphere warms or cools depending upon the feed rate of ozone. The feed rate changes over time.

The ozone content and temperature of the upper stratosphere depends in the first instance upon the activity of the night jet at the poles that introduces NOx from the mesosphere. Less NOx means more ozone. The activity of the night jet depends upon surface pressure and the concentration of NOx in the jet depends upon solar activity. In Antarctica, surface pressure has been falling for sixty years indicating a continuous increase in the ozone feed into the troposphere, the second major influence upon the ozone content of the polar stratosphere.

In that the coupled circulation of the stratosphere and the troposphere over Antarctica changes surface pressure at 60-70° south it changes the strength of the westerly winds in the southern hemisphere, cloud cover and surface temperature on all time scales. Stratospheric ozone is wasted above and below the stratosphere, processes referred to as ‘unknown dynamical influences’ in the more respectable polar ozone studies.

These phenomena are the very essence of the Southern Annular Mode, arguably the fundamental mode of global climate variation on all time scales.

One thing is plain. High altitude ice cloud in the southern hemisphere is plainly a reflector of solar radiation. It does not promote warming (positive feedback). It promotes cooling (negative feedback). It’s presence depends upon the flux in ozone in the upper troposphere as governed by processes in the stratosphere. So the UNIPCC climate models are 180° out of whack.

If your brain is starting to hurt, just rest it for a moment while you consider the following.

I wandered lonely as a cloud

That floats on high o’er vales and hills,

When all at once I saw a crowd,

A host, of golden daffodils;

Beside the lake, beneath the trees,

Fluttering and dancing in the breeze.

Continuous as the stars that shine

And twinkle on the milky way,

They stretched in never-ending line

Along the margin of a bay:

Ten thousand saw I at a glance,

Tossing their heads in sprightly dance.

The waves beside them danced; but they

Out-did the sparkling waves in glee:—

A poet could not but be gay

In such a jocund company:

I gazed—and gazed—but little thought

What wealth the show to me had brought.

For oft when on my couch I lie

In vacant or in pensive mood,

They flash upon that inward eye

Which is the bliss of solitude,

And then my heart with pleasure fills,

And dances with the daffodils…

When we were in the woods beyond Gowbarrow park we saw a few daffodils close to the water side, we fancied that the lake had floated the seeds ashore & that the little colony had so sprung up— But as we went along there were more & yet more & at last under the boughs of the trees, we saw that there was a long belt of them along the shore, about the breadth of a country turnpike road . . . [S]ome rested their heads on [mossy] stones as on a pillow for weariness & the rest tossed & reeled & danced & seemed as if they verily laughed with the wind that blew upon them over the Lake, they looked so gay ever glancing ever changing. This wind blew directly over the lake to them. There was here & there a little knot & a few stragglers a few yards higher up but they were so few as not to disturb the simplicity & unity & life of that one busy highway… —Rain came on, we were wet. William Wordsworth 1815

Now that you have rested you might devise a mathematical model that mimics the behavior of the climate system as described in this post.