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March-April 2014

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The Winds of Islam

The religion of Islam is based on the divine revelations of the holy prophet Mohammed. As a historical figure, scholars state that Mohammed's religious calling began around the age of 40 (about the year 640 Common Era or C.E.) when he was first visited by the archangel Gabriel. Gabriel's words become the initial verses of the Islamic holy book, the Koran or Qur'an. Following those and additional revelations, Mohammed became a revered leader who unified the peoples of Arabia into a single religious polity under the banner of Islam.

From a scientific viewpoint, it is enlightening to examine the suras (chapters) of the Koran and additional Islamic writings for evidence of environmental knowledge and events. Two key battles that occurred early in the rise of Islam across the Middle East were influenced by weather. The first is the famous Battle of Badr, which was fought on Saturday, March 13, 624 C.E.

The Battle of Badr's Dust Storm

The historical setting for the Battle of Badr follows Mohammed and his followers' migration (Hijra) from Mecca to Medina resulting from persecution due to his monotheistic teachings. Those teachings provoked death threats from the more socially and economically powerful polytheists, known as the Quraysh, who controlled Mecca at that time. After the holy prophet and his followers established themselves in Medina, relations between the two Arabian communities became increasingly strained, and by the year 623 C.E., hostilities had broken out when Mohammed's Muslim forces began to initiate raids or limited battles (ghazawat in Arabic) on the Meccans' rich and lucrative trading caravans. Although the desert tribes at the time did have a tradition of raiding each other, the ghazawat of the Muslims under the command of Mohammed began to experience increasing success against the their prosperous Quraysh adversaries. The holy prophet himself even began to lead some of the raiding parties. As their wealth and prosperity began to decline under the face of the attacks, the Quraysh desperately searched for an opportunity to end the ruinous raids.

In the spring of 624 C.E., Mohammed received word from his spies that a very rich trading caravan under the leadership of (at the time) one of the prophet's enemies, Abu Sufyan ibn Harb, was en route to Mecca. In response, Mohammed gathered an army of over 300 warriors—the largest army his forces had ever assembled up to that time. However, the Quraysh, having heard of the raiding party, countered with a huge army of nearly 1,000 warriors, with most mounted on camels—an overwhelming force that suggested an easy victory over the raiders and which perhaps could end Mohammed's increasing popularity.

The two armies converged at the oasis of Badr, about 130 kilometers from Medina, on the Syrian trade route. The oasis of Badr is located on the eastern slope of a broad valley. The western side of the valley is marked in by a large hill. The prophet's Muslim raiders reached the oasis of Badr first and took control of the area. They filled in all but one of the water wells (so that the enemy couldn't use them) while their opponents camped on the slopes of the hill to the west. It was at this stage that weather began to exert an influence on the battle.

When drowsiness covered you as a security from Allah, and Allah sent down upon you from the heavens water to purify you withal, and to take away from you the plague of Shaitan [the Devil], and to tie up your hearts and to make firm your footsteps. [Qur'an, sura 8 (al-'Alfal; the Spoils of War), ayah 11]

According to Muslim sources, the ayah (verse) above suggest that a heavy thunderstorm with rain broke over the area the night before the battle—likely preventing any attempt at a sneak attack from the Quraysh and allowing the Muslim defenders to peacefully rest. Then, because the Muslims held the high eastern slopes, the next morning the Quraysh were forced to march down the wet mud and sand slopes through the worst portions of the valley before having to march up the eastern side of the valley. As a result, the sun (and likely the heat) was rising by the time the Quraysh crested the eastern side of the valley summit. By that time, the rains and heat would likely have firmly packed the loose sand in the eastern valley. This helped the Muslims plant their feet firmly and facilitated their battle positioning.

Map of the Battle of Badr.

After a set of preliminary one-on-one matches, general conflict between the two forces began with arrow volleys and then hand-to-hand sword-work. Things appeared bleak for the outnumbered Muslims when, according the Koran, thousands of angels then descended to help the besieged followers of Mohammed, and the Quraysh were forced to withdraw to regain their strength. However, it is at this time that that second environmental power exerted by the holy prophet also occurs:

And you did not kill them, but it was Allah who killed them. And you threw not, O Mohammed, when you threw [the dust], but it was Allah who threw that He might test the believers with a good test. [Qur'an, sura 8 (al-'Alfal; the Spoils of War), ayah 17]

Following the words of the Biblical prophet Hosea, who proclaimed, “For they have sown the wind, and they shall reap the whirlwind” (Hosea 8:7), Mohammed used the desert power of wind and dust in the Battle of Bahr. The founder of Islam supposedly created a monster dust storm by merely picking up a handful of sand and flinging it toward his enemies with a curse. As he and his troopers sprinted towards his enemies, the tiny whirlwind that he had created grew in size, tore across the desert, and swept with full fury into the Quraysh swordsmen. In a few minutes the enemy was so blinded and confused by the unexpected dust that most of them turned around in frustrated retreat. The holy Islamic prophet's first major victory was assured.

But is this set of environmental events possible?

Actually, it is. First, desert storms are often quite severe. The layout of the Badr battlefield—with the memorial to the very few fallen Muslims—indicates that the end of the battle did occur on the western side of the Badr valley, verifying the idea that the last part of the battle was associated with a surge by the Muslims. But recall from the thunderstorm mentioned above that the west side of the valley is much more sandy, opening to a huge desert to the northwest. If the thunderstorms had occurred in the immediate vicinity the night before, it is possible that thunderstorms away from the battlefield during the day of the battle blew out violent winds, the final remains of those more distant thunderstorms, and then slammed into the valley containing the oasis of Badr. Those strong winds rushing over the sand dunes to the northeast of Badr could easily generate a violent dust storm.

Map of the Medina Battle of the Trench.

Indeed, in the American Southwest, that type of situation occurs frequently. In the late heat of the day, thunderstorms build over southern Arizona. Downbursts from such storms after they collapse spread out like bomb blasts over the desert floors. Sometime later, such winds may lift massive amounts of dust into the air creating what is called a haboob—actually an Arabic term for exactly the type of a dust wall that may have been blown into the Battle of Badr.

For example, on July 5, 2011, Phoenix, Arizona, was struck by a mammoth haboob—a gigantic wall of dust that stretched for over 100 miles and extended upwards over 5,000 feet. Consequently, from a meteorological viewpoint at least, the environmental results of massive desert haboobs are not out of line with legends of the divinely inspired dust storm at the Battle of Badr.

The Battle of the Trench and the Greenhouse Effect

Meteorology might have also played a central role in a later conflict that occurred three years after the Battle of Badr. To a meteorologist, three surprisingly modern weather concepts can be applied to understanding how the horrendous siege of the Muslim-held city of Medina in the year 627 C.E. was shattered and the besieged Muslims under the prophet Mohammed emerged victorious. Those three concepts involve our scientific understanding of the “greenhouse effect,” “continentality,” and the “urban heat island” effect.

When we imagine desert regions, our perceptions tend to focus on two basic conditions: heat and aridity. Ask almost any resident of a desert city for a typical weather forecast and two words are common: “hot” and “dry.” But, relatively unknown to most non-desert dwellers, the desert is also known for its coldness—particularly at night. Why? It has to do with water.

Water holds heat. Water in its gaseous state—water vapor—is actually a very effective “greenhouse gas.” Scientifically, greenhouse gases are those gases that act to absorb and re-emit the long-wave or terrestrial radiation—the earth's heat—of our planet. The effectiveness of water vapor as a greenhouse gas is easily proven with a simple observation: Is it warmer on a still cloudy night or on a still clear night? The answer, that a still cloudy night is warmer, points to the fact that those clouds—water and water vapor in our sky—act to keep a good portion of the heat emitted from the ground from escaping into space.

But what does water vapor have to do with the desert? This brings in the idea of “continentality.” Remember atmospheric water vapor holds heat. Remove that water vapor from the air, and the heat from the ground can rapidly escape into space. Deserts are, in general, far from oceans and therefore dry, and so the intense heat captured by the sands during the hot days can quickly dissipate during the night. Therefore, during the night the deserts become very cold! That concept—that desert locations due to their lack of humidity will experience much colder (and, during the day, warmer) conditions than their coastal counterparts—is called “continentality.”

The third modern meteorological concept that influenced the medieval Battle of the Trench is that of the “urban heat island.” The urban heat island is a concept that actually dates back to the days of the American Revolutionary War, when the statesman and lexicographer Noah Webster noticed in the late 1700s that the center of New York City was consistently several degrees warmer than the rural outskirts.

Since that time, climatologists have proven that Webster was unmistakably right—urban areas are consistently warmer than their rural counterparts. And they determined the reason why. Remember that water is effective at holding (absorbing) heat; it has a high “heat capacity.” Every material has its own particular heat capacity. Two common urban materials, asphalt and concrete, have higher heat capacities than normal soil; that means they can absorb more heat than normal soil can. So during the day, they store more heat than the rural soil and vegetation. During the evening, that extra heat is released—and the city is warmer than it would be otherwise.

The temperature difference between warmer urban areas and colder rural locations is particularly pronounced in the arid deserts of the world—areas where the competing and obscuring influences of water vapor (remember the greenhouse effect discussion) are limited or absent. In Phoenix, Arizona, for example, the center of the city (where Sky Harbor International Airport is located) is often five to seven degrees Fahrenheit warmer than the desert surroundings.

So, in summary, due to lack of humidity, deserts can cool down significantly at night. But, due to the urban heat effect, desert cities will be noticeably warmer than their surrounding sandy deserts.

The Battle of the Trench, sometimes referred to as the Siege of Medina or the Battle of Ahzab, occurred three years after the prophet Mohammed's victory at Badr over the Quraysh, the people in control of Mecca. Other than a few skirmishes after the Battle of Badr, an uneasy military stalemate had existed between the two powers on the Sinai Peninsula for the next three years.

Finally in 627 C.E., in response to Mohammed's increasing appeal to the Bedouins and coastal communities, a massive army of 10,000 Quraysh—especially reinforced by mounted cavalry—and their allies (nicknamed al-'Ahzab or “the Confederacy”) marched to Medina in late March and besieged the city. However, Mohammed had learned of the advancing army and quickly devised a particularly ingenious defense. He protected the central part of the area by digging a huge, deep trench around the city—an obstacle that the mounted Quraysh cavalry simply could not cross! With the significant advantage of their mounted warriors nullified, the Confederate Meccan forces under the command of the Quraysh were forced to settle in for a long siege.

Remember the favor of Allah towards you when great hosts came against you, and We sent against them a wind and hosts whom you did not see. [Qur'an, sura 33 (al-'Aĥzāb, the Confederacy), ayah 9]

After the Quraysh Confederacy began its siege of Medina, Islamic sources say that the desert nights outside of the city for the next two weeks were piercingly cold with a bleak easterly wind. The besieging Confederate forces that were camped outside the city walls were in increasingly dire straits. The nightly bitter winds were shredding their tents, extinguishing their campfires, and overturning their cooking pots. Even the Confederacy's horses and camels were suffering and dying.

Meteorologically, an easterly wind makes sense for these apparently frigid cold conditions in Arabia. Weather is driven by massive pressure systems, termed “highs” and “lows,” that circulate air around them. In the Northern Hemisphere, air around a high pressure system rotates clockwise. If the center of an arctic high pressure system was to sink as far south as the eastern Mediterranean Sea and Turkey, cold polar air originating from northern Russia could rotate into Arabia—as an easterly wind!

Such cold events are not unknown in the Middle East of today's world. During the bitterly cold month of March 2012, for example, snow fell in the city of Jerusalem, Israel—and even in parts of Saudi Arabia—while night temperatures across the Middle East were consistently below 50°F. The effects of continentality—the lack of humidity in these deserts—were undoubtedly magnifying those cold conditions. Imagine being forced to be live in inadequate tents at night in the exposed desert under such conditions. Arab scholars have concluded that the Confederate forces of the Quraysh in 627 C.E. outside of Medina suffered tremendously due to such cold conditions.

Yet conditions in the besieged city of Medina itself for the prophet Mohammed and his Islamic forces apparently weren't that dire. Remember that the basic building materials of the city (not modern concrete and asphalt, of course, but other materials such as adobe and rock) would help to hold in the limited heat of the sun, so it wasn't as cold in Medina as it was in the surrounding area. In addition, the walls of the city and its buildings would disrupt the chilling easterly wind flow. The warming effect of the urban heat island directly aided the besieged city dwellers.

Meanwhile, outside the city, the invaders were growing increasingly disheartened. Finally, in recognition of the brutally bitter conditions, their leader deemed that the hardships were too much for the troops, and within the course of a single night, the whole Confederate army withdrew, lifting the siege. The long-term results of the failure of the Quraysh siege of Medina cemented Mohammed's political leadership in the city of Medina. On the other hand, the Quraysh of Mecca lost their lucrative trade with Syria—and their decline as a political force in the region had begun.

From a meteorological standpoint, was the outcome of the Battle of the Trench the result in part of the weather constraints imposed by the greenhouse effect, continentality, and the urban heat island? Certainly Arab scholars suggest that the intense evening cold, bitter winds and the resulting hardships influenced the decisions of the Confederate commander Abu Sufyan ibn Harb in dropping the siege. And the fact that the Muslim defenders were in good enough condition after the fight to attack and capture one of the Confederate tribes soon after the lifting of the siege implies that perhaps the conditions within the besieged city of Medina were at least in part mitigated by the warmth of the urban heat effect. Consequently, it appears that the early rise and growth of the Islamic religion was, at least in part, influenced by the desert winds and arid environment of Arabia.

RANDY CERVENY is a President's Professor of Geographical Sciences at Arizona State University and a contributing editor of Weatherwise.

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